Biopharmconsortium Blog

Expert commentary from Haberman Associates biotechnology and pharmaceutical consulting.

Posts filed under: Strategy and Consulting

Our New Year’s 2015 article: Notable researchers and breakthrough research of 2014


Pre-1917 Russian Happy Christmas and Happy New Year card

Pre-1917 Russian Happy Christmas and Happy New Year card

As is their customary practice, both Nature and Science ran end-of-year specials. The Nature special (in their 18 December issue) is entitled “365 days: Nature’s 10. Ten people who mattered this year.” The Science special (in their 19 December issue) is entitled, as usual “2014 Breakthrough of the Year.” As is also usual, there is a section for “Runners Up” to the year’s “Breakthrough”.

From the point of view of a consulting group—and a blog—that focuses on effective drug discovery and development strategies, we were disappointed with both end-of-year specials. Most of the material in these articles was irrelevant to our concerns.

Science chose the Rosetta/Philae comet-chasing mission as the “Breakthrough of the Year”, and its “runners up” included several robotics and space-technology items, as well as new “letters” to the DNA “alphabet” that don’t code for anything.

Nature also focused on comet chasers, robot makers, and space technologists, as well as cosmologist and mathematicians, and a fundraising gimmick—“the ice-bucket challenge”. Moreover, Nature was much too restrictive in titling its article “Ten people who mattered”. Every human being matters!

Nevertheless, these two special sections do contain a few gems that are both relevant to effective drug discovery and development, and are worthy of highlighting as “notable researchers of 2014” and “breakthrough research of 2014”. We discuss these in the remainder of this article.

Suzanne Topalian, M.D.

Suzanne Topalian is one of the researchers profiled in “Nature’s 10”. She is a long-time cancer immunotherapy clinical researcher who began her career in 1985 in the laboratory of cancer immunotherapy pioneer Steven Rosenberg at the National Cancer Institute (Bethesda MD). In the early days of the field, when cancer immunotherapy was scientifically premature, there was a great deal of skepticism that these types of treatments would even work. However, both Dr. Rosenberg and Dr. Topalian persevered in their research.

In 2006, Dr. Topalian moved to Johns Hopkins University (Baltimore, MD) to help launch clinical trials of Medarex/Bristol-Myers Squibb/Ono’s nivolumab, a PD-1 inhibitor. As noted in the Nature article, her work “led to a landmark publication in 2012 showing that nivolumab produced dramatic responses not only in some people with advanced melanoma but also in those with lung cancer [specifically, non–small-cell lung cancer, NSCLC].” We also discussed that publication on the Biopharmconsortium Blog, and in our recently published book-length Insight Pharma Report, Cancer Immunotherapy: immune checkpoint inhibitors, cancer vaccines, and adoptive T-cell therapies. Our report also includes discussions of Dr. Rosenberg’s more recent work in cellular immunotherapy.

As discussed in our report, nivolumab was approved in Japan as Ono’s Opdivo in July 2014 for treatment of unresectable melanoma, and a competitive PD-1 inhibitor, pembrolizumab (Merck’s Keytruda) was approved in the United States for advanced melanoma on September 5, 2014. More recently, on December 22, 2014, the FDA also approved nivolumab (BMS’ Opdivo) for advanced melanoma in the U.S. There are thus now two FDA-approved PD-1 inhibitors [in addition to the CTLA-4 inhibitor ipilimumab (BMS’ Yervoy)] available for treatment of advanced melanoma in the U.S.

Meanwhile, researchers continue to test both nivolumab and pembrolizumab for treatment of NSCLC and other cancers. And some analysts project that both of these agents are likely to be approved by the FDA for treatment of various populations of patients with NSCLC before the middle of 2015. Researchers are also testing combination therapies that include nivolumab or pembrolizumab in various cancers. And clinical trials of Genentech/Roche’s PD-L1 blocking agent MPDL3280A are also in progress.

Science’s 2013 Breakthrough of the Year was cancer immunotherapy, as we highlighted in our New Year’s 2014 blog article. Science could not make cancer immunotherapy the Breakthrough of the Year for 2014, too. Thus it chose to give physical scientists a turn in the limelight by highlighting the comet-chasing mission instead. Nevertheless, 2014 was the year in which cancer immunotherapy demonstrated its maturity by the regulatory approval of the two most advanced checkpoint inhibitor agents, pembrolizumab and nivolumab.

Implications for patients with terminal cancers

The clinically-promising results of cancer immunotherapy in a wide variety of cancers, coupled with the very large numbers of clinical trials in progress in this area, has also changed the situation for patients who have terminal cancers. Researchers who are conducting clinical trials of immunotherapies for these cancers are actively recruiting patients, of whom there are limited numbers at any one time. For example, there are now numerous clinical trials—mainly of immunotherapies—in pancreatic cancer, and most of these trials are recruiting patients. There are also active clinical trials of promising immunotherapies in the brain tumor glioblastoma. These are only two of many examples.

Recently, a 29-year-old woman with terminal glioblastoma ended her life using Oregon’s physician-assisted suicide law. Prior to her suicide, she became an advocate for “terminally ill patients who want to end their own lives”. We, however, are advocating that patients with glioblastoma and other types of terminal cancer for which there are promising immunotherapies seek out clinical trials that are actively recruiting patients. There is the possibility that some of these patients will receive treatments that will result in regression of their tumors or long-term remissions. (See, for example, the case highlighted in our September 16, 2014 blog article. There are many other such cases.) And it is highly likely that patients who participate in these trials will help researchers to learn how to better treat cancers that are now considered “incurable” or “terminal”, and thus help patients who contract these diseases in the future. From our point of view, that is a lot better than taking one’s own life via assisted suicide, and/or becoming an euthanasia advocate.

Masayo Takahashi, M.D., Ph.D.

Another researcher profiled in “Nature’s 10” is Masayo Takahashi, an ophthalmologist at the RIKEN Center for Developmental Biology (CDB) in Kobe, Japan who has been carrying out pioneering human stem cell clinical studies. We also discussed Dr. Takahashi’s research in our March 14, 2013 article on this blog.

At the time of our article, Dr. Takahashi and her colleagues planned to submit an application to the Japanese health ministry for a clinical study of induced pluripotent stem cell (iPS)-derived cells, which would constitute the first human study of such cells. They planned to treat approximately six people with severe age-related macular degeneration (AMD). The researchers planned to take an upper arm skin sample the size of a peppercorn, and transform the cells from this sample into iPS cells by using specific proteins. They were then to add other factors to induce differentiation of the iPS cells into retinal cells. Then a small sheet of these retinal cells were to be placed under the damaged area of the retina, where they were expected to grow and repair the damaged retinal pigment epithelium (RPE). Although the researchers would like to demonstrate efficacy of this treatment, the main focus of the initial studies was to be on safety.

According to the “Nature’s 10” article, such an autologous iPS-derived implant was transplanted into the back of a the damaged retina of one patient in September 2014. This patient, a woman in her 70s, had already lost most of her vision, and the treatment is unlikely to restore it. However, Dr. Takahashi and her colleagues are determining whether the transplant is safe and prevents further retinal deterioration. So far, everything has gone smoothly, and the transplant appears to have retained its integrity. However, the researchers will not reveal whether the study has been a success until a year after the transplantation.

The “Nature’s 10” article discusses how this technology might be moved forward into clinical use if the initial study is successful. It also discusses how Dr. Takahashi has been carrying her research forward in the face of a major setback that has plagued stem cell research at the CDB in 2014, as the result of the withdrawal of two once highly-regarded papers and the suicide of one of their authors.

Generation of insulin-producing human pancreatic β cells from embryonic stem (ES) cells or iPS

Another stem cell-related item, which was covered in Science’s end-of-2014 “Runners Up” article, concerned the in vitro generation of human pancreatic β cells from embryonic stem (ES) cells or iPS. For over a decade, researchers have been attempting to accomplish this feat, in order to have access to autologous β cells to treat type 1 diabetes, in which an autoimmune attack destroys a patient’s own β cells. In vitro generated β cells might also be used to screen for drugs that can improve β cell function, survival, and/or proliferation in patients with type 2 diabetes.

As reported in the Science article, two research groups—one led by Douglas A. Melton, Ph.D. (Harvard Stem Cell Institute, Cambridge, MA), and the other by Alireza Rezania, Ph.D. at BetaLogics Venture, a division of Janssen Research & Development, LLC.–developed protocols to produce unlimited quantities of β cells, in the first case from IPS cells, and in the other from ES cells.

However, in order to use the β cells to treat type 1 diabetes patients, researchers need to develop means (for example, some type of encapsulation) to protect the cells from the autoimmune reaction that killed patients’ own natural β cells in the first place. For example, Dr. Melton is collaborating with the laboratory of Daniel Anderson, Ph.D. (MIT Koch Institute for Integrative Cancer Research). Dr. Anderson and his colleagues have developed a chemically modified alginate that can be used to coat and protects clusters of β cells, thus forming artificial islets. Dr. Melton estimates that such implants would be about the size of a credit card.

The 2014 Boston biotech IPO boom

Meanwhile, the Boston area biotechnology community has seen a boom in young companies holding their initial public offerings (IPOs). 17 such companies were listed in a December 24 article in the Boston Business Journal. Among these companies are three that have been covered in the Biopharmconsortium Blog—Zafgen, Dicerna, and Sage Therapeutics.

We hope that 2015 will see at least the level of key discoveries, drug approvals, and financings seen in 2014.

As the producers of this blog, and as consultants to the biotechnology and pharmaceutical industry, Haberman Associates would like to hear from you. If you are in a biotech or pharmaceutical company, and would like a 15-20-minute, no-obligation telephone discussion of issues raised by this or other blog articles, or of other issues that are important to your company, please contact us by phone or e-mail. We also welcome your comments on this or any other article on this blog.

Cancer Immunotherapy Report Published By CHI Insight Pharma Reports

T cells attached to tumor cell. Source: MSKCC.

T cells attached to tumor cell. Source: MSKCC.


On September 9, 2014, Cambridge Healthtech Institute’s (CHI’s) Insight Pharma Reports announced the publication of a new book-length report, Cancer Immunotherapy: Immune Checkpoint Inhibitors, Cancer Vaccines, and Adoptive T-cell Therapies, by Allan B. Haberman, Ph.D.

As attested by the torrent of recent news, cancer immunotherapy is a “hot”, fast-moving field. For example:

  • On September 5, 2014, the FDA granted accelerated approval to the PD-1 inhibitor pembrolizumab (Merck’s Keytruda, also known as MK-3475) for treatment of advanced melanoma. This approval was granted nearly two months ahead of the agency’s own deadline. Pembrolizumab is the first PD-1 inhibitor to reach the U.S. market.
  • On May 8, 2014, the New York Times published an article about a woman in her 40’s who was treated with adoptive immunotherapy with autologous T cells to treat her cancer, metastatic cholangiocarcinoma (bile-duct cancer). This deadly cancer typically kills the patient in a matter of months. However, as a result of this treatment, the patient lived for over 2 years, with good quality of life, and is still alive today.

These and other recent news articles and scientific publications attest to the rapid progress of cancer immunotherapy, a field that only a few years ago was considered to be impracticable.

Our report focuses on the three principal types of therapeutics that have become the major focuses of research and development in immuno-oncology in recent years:

  • Checkpoint inhibitors
  • Therapeutic anticancer vaccines
  • Adoptive cellular immunotherapy

The discussions of these three types of therapeutics are coupled with an in-depth introduction and history as well as data for market outlook.

Also featured in this report are exclusive interviews with the following leaders in cancer immunotherapy:

  • Adil Daud, MD, Clinical Professor, Department of Medicine (Hematology/Oncology), University of California at San Francisco (UCSF); Director, Melanoma Clinical Research, UCSF Helen Diller Family Comprehensive Cancer Center.
  • Matthew Lehman, Chief Executive Officer, Prima BioMed (a therapeutic cancer vaccine company with headquarters in Sydney, Australia).
  • Marcela Maus, MD, PhD, Director of Translational Medicine and Early Clinical Development, Translational Research Program, Abramson Cancer Center, University of Pennsylvania in Philadelphia.

The report also includes the results and an analysis of a survey of individuals working in immuno-oncology R&D, conducted by Insight Pharma Reports in conjunction with this report. The survey focuses on market outlook, and portrays industry opinions and perspectives.

Our report is an in-depth discussion of cancer immunotherapy, an important new modality of cancer treatment that may be used to treat as many as 60% of cases of advanced cancer by the late 2010s/early 2020s. It includes updated information from the 2014 ASCO (American Society of Clinical Oncology) and AACR (American Association for Cancer Research) meetings. The report is designed to enable you to understand current and future developments in immuno-oncology. It is also designed to inform the decisions of leaders in companies and in academic groups that are working in areas that relate to cancer R&D and treatment.

For more information on Cancer Immunotherapy: Immune Checkpoint Inhibitors, Cancer Vaccines, and Adoptive T-cell Therapies, or to order it, see the Insight Pharma Reports website.


As the producers of this blog, and as consultants to the biotechnology and pharmaceutical industry, Haberman Associates would like to hear from you. If you are in a biotech or pharmaceutical company, and would like a 15-20-minute, no-obligation telephone discussion of issues raised by this or other blog articles, or of other issues that are important to your company, please contact us by phone or e-mail. We also welcome your comments on this or any other article on this blog.

Forma Therapeutics’ expanded R&D collaboration with Celgene


Ubiquitin pathway. Source: Rogerdodd, English language Wikipedia

Ubiquitin pathway. Source: Rogerdodd, English language Wikipedia

On April 1, 2014, Forma Therapeutics (Watertown MA) announced that it had entered into an expanded strategic collaboration with Celgene (Summit, NJ).

Under the new agreement, Forma has received an upfront cash payment of $225 million. The initial collaboration between the two companies under the new agreement will be for 3 1⁄2 years. Celgene will also have the option to enter into up to two additional collaborations with terms of two years each for additional payments totaling approximately $375 million. Depending on the success of the collaborations and if Celgene elects to enter all three collaborations, the combined duration of the three collaborations may be at least 7 1⁄2 years.

Under the terms of the new agreement, Forma will control projects from the research stage through Phase 1 clinical trials. For programs selected for licensing, Celgene will take over clinical development from Phase 2 to commercialization. Forma will retain U.S. rights to these products, and Celgene will have the rights to the products outside of the U.S. For products not licensed to Celgene, FORMA will maintain worldwide rights.

During the term of the third collaboration, Celgene will have the exclusive option to acquire Forma, including the U.S. rights to all licensed programs, and worldwide rights to other wholly owned programs within Forma at that time.

The April 2013 agreement between Forma and Celgene

The new collaboration between Forma and Celgene builds on an earlier agreement between the two companies. On April 29, 2013, the two companies entered into a collaboration aimed at discovery, development, and commercialization of drug candidates to modulate targets involved in protein homeostasis.

Protein homeostasis, also known as proteostasis, involves a tightly regulated network of pathways controlling the biogenesis, folding, transport and degradation of proteins. The ubiquitin pathway (illustrated in the figure above) is one of these pathways. We recently discussed how the ubiquitin pathway is involved in the mechanism of action of thalidomide and lenalidomide (Celgene’s Thalomid and Revlimid).

Targeting protein homeostasis has application to discovery and development of drugs for oncology, neurodegenerative disease, and other disorders. However, the April 2013 Forma/Celgene agreement focused on cancer. Under that agreement, Forma received an undisclosed upfront payment. Upon licensing of preclinical drug candidates by Celgene, Forma was to be eligible to receive up to $200 million in research and early development payments. FORMA was also to be eligible to receive $315 million in potential payments based upon development, regulatory and sales objectives for the first ex-U.S. license, as well as  up to a maximum of $430 million per program for further licensed products, in addition to post-sales royalties.

On October 8, 2013, Forma announced that it had successfully met the undisclosed first objective under its April 2013 strategic collaboration agreement with Celgene. This triggered an undisclosed payment to Forma. Progress in the April 2013 collaboration was an important basis for Celgene’s decision to enter into a new, broader collaboration with Forma a year later.

The scope of the new April 2014 Forma/Celgene collaboration

Unlike the April 2013 agreement, the April 2014 agreement between Forma and Celgene is not limited to protein homeostasis, or to oncology. The goal of the new collaboration is to “comprehensively evaluate emerging target families for which Forma’s platform has exceptional strength” over “broad areas of chemistry and biology”.  The expanded collaboration will thus involve discovery and development of compounds to address a broad range of target families and of therapeutic areas.

According to Celgene’s Thomas Daniel, M.D. (President, Global Research and Early Development), Celgene’s motivation for signing the new agreement is based not only on the early success of the existing Forma/Celgene collaboration, but also on “emerging evidence of the power of Forma’s platform to generate unique chemical matter across important emerging target families”.

According to Forma’s President and CEO, Steven Tregay, Ph.D., the new collaboration with Cegene enables Forma to maintain its autonomy in defining its research strategy and conducting discovery through early clinical development. It also aligns Forma with Celgene’s key strengths in hematology and in inflammatory diseases.

Forma Therapeutics in Haberman Associates publications

We have been following Forma on the the Biopharmconsortium Blog since July 2011. At that time, I was a speaker at Hanson Wade’s World Drug Targets Summit (Cambridge, MA). At that meeting, Mark Tebbe, Ph.D. (then Vice President, Medicinal and Computational Chemistry at Forma) was also a speaker. At the conference, Dr. Tebbe discussed FORMA’s technology platforms, which are designed to be enabling technologies for discovery of small-molecule drugs to address challenging targets such as protein-protein interactions (PPIs).

In particular, Dr. Tebbe discussed Forma’s Computational Solvent Mapping (CS-Mapping) platform, which enables company researchers to interrogate PPIs in intracellular environments, to define hot spots on the protein surfaces that might constitute targets for small-molecule drugs. FORMA has been combining CS-Mapping technology with its chemistry technologies (e.g., structure guided drug discovery, diversity orientated synthesis) for use in drug discovery.

We also discussed Forma’s earlier fundraising successes as of January 2012, and cited Forma as a “built to last” research-stage platform company in an interview for Chemical & Engineering News (C&EN).

Finally, we discussed Forma and its technology platform in our book-length report, Advances in the Discovery of Protein-Protein Interaction Modulators, published by Informa’s Scrip Insights in 2012. (See also our April 25, 2012 blog article.)

In our report, we discussed Forma as a company that employs “second-generation technologies” for the discovery of small-molecule PPI modulators. This refers to a suite of technologies designed to overcome the hurdles that stand in the way of the accelerated and systematic discovery and development of PPI modulators. Such technologies are necessary to make targeting of PPIs a viable field.

Forma’s website now has a brief explanation of its drug discovery engine, as it is applied to targeting PPIs. This includes links to web pages describing:

Our 2012 book-length report discusses technologies of these types, as applied to discovery of PPI modulators, in greater detail than the Forma website.

According to Dr. Daniel: “Progress in our existing [protein homeostasis] collaboration, coupled with emerging evidence of the power of FORMA’s platform to generate unique chemical matter across important emerging target families” led Celgene to enter into its new, expanded collaboration with Forma in April 2014. This suggests that Celgene is especially impressed by Forma’s chemistry and chemical biology platforms. it also suggests that chemistry technology platforms developed to address PPIs may be applicable to areas of drug discovery beyond PPIs as well.

Concluding remarks

Despite the enthusiasm for Forma and its drug discovery engine shown by Celgene, Forma’s other partners, and various industry experts, it must be remembered that Forma is still a research-stage company. The company has not one lone drug candidate in the clinic, let alone achieving proof-of-concept in humans. It is clinical proof-of-concept, followed by Phase 3 success and approval and marketing of the resulting drugs, that is the “proof of the pudding” of a company’s drug discovery and development efforts.

We await the achievement of such clinical milestones by Forma Therapeutics.

From a business strategy point of view, we have discussed Forma’s efforts to build a stand-alone, independent company for the long term in this blog and elsewhere. Now Forma has entered into an agreement with Celgene that might—in around 7-10 years—result in Forma’s acquisition. This would seem to contradict Forma’s “built to last” strategy.

However, in the business environment that has prevailed over the past several years, several established independent biotech companies, notably Genentech and Genzyme, have been acquired by larger companies. Even several Big Pharmas (e.g., Schering-Plough and Wyeth) have been acquired.

Nevertheless, we do not know what the business environment in the biotech/pharma industry will be like in 7-10 years, despite the efforts of strategists to predict it. And Celgene might forgo its option to acquire Forma, for any number of reasons. So the outlook for Forma’s status as an independent or an acquired company (which also depends on its success in developing drugs) is uncertain.


As the producers of this blog, and as consultants to the biotechnology and pharmaceutical industry, Haberman Associates would like to hear from you. If you are in a biotech or pharmaceutical company, and would like a 15-20-minute, no-obligation telephone discussion of issues raised by this or other blog articles, or of other issues that are important to  your company, please contact us by phone or e-mail. We also welcome your comments on this or any other article on this blog.

RNAi therapeutics stage a comeback

Transthyretin protein structure

Transthyretin protein structure

Not so long ago, the once-promising field of RNA interference (RNAi)-based drugs was on the downswing. This was documented in our August 22, 2011 article on this blog, entitled “The Big Pharma Retreat From RNAi Therapeutics Continues”. That article discussed the retreat from RNAi drugs by such Big Pharma companies as Merck, Roche, and Pfizer. In our March 30, 2012 blog article, we also mentioned leading RNAi company Alnylam’s (Cambridge, MA) January 20, 2012 downsizing. This restructuring was made necessary by Alnylam’s inability to continue capturing major Big Phama licensing and R&D deals, as it had once done.

As we discussed in our August 22, 2011 article, the therapeutic RNAi (and microRNA) field represented an early-stage area of science and technology, which may well be technologically premature. This level of scientific prematurity was comparable to that of the monoclonal antibody (MAb) drug field in the 1980s. Big Pharmas did not have the patience to continue with the RNAi drug programs that they started.

In that article, we cited an editorial by oligonucleotide therapeutics leader Arthur Krieg, M.D. This editorial discussed the issues of therapeutic RNAi’s scientific prematurity, but predicted a rapid upswing of the field once the main bottleneck–oligonucleotide drug delivery–had been validated.

The January 2014 Alnylam-Genzyme/Sanofi deal

Now–as of January 2014–there is much evidence that the therapeutic RNAi field is indeed coming back. This is especially true for Alnylam. On January 13, 2014, it was announced that Genzyme (since 2011 the rare disease unit of Sanofi) invested $700 million in Alnylam’s stock. Alnylam called this deal “transformational” for both Alnylam and the RNAi therapeutics field.

Genzyme had previously been a partner in developing Alnylam’s lead product patisiran (ALN-TTR02) for the treatment of transthyretin-mediated amyloidosis (ATTR). [ATTR is a rare inherited, debilitating, and often fatal disease caused by mutations in the transthyretin (TTR) gene.] Under the new agreement, Genzyme will gain marketing rights to patisiran everywhere except North America and Western Europe upon its successful completion of clinical trials and approval by regulatory agencies. Genzyme will also codevelop ALN-TTRsc, a subcutaneously-delivered formulation of patisiran. Intravenously-delivered patisiran is now in Phase 3 trials for a form of ATTR known as familial amyloidotic polyneuropathy (FAP), and ALN-TTRsc is in Phase 2 trials for a form of ATTR known as familial amyloidotic cardiomyopathy (FAC).

The Alnylam/Genzyme deal will also cover any drugs in Alnylam’s pipeline that achieve proof-of-concept before the end of 2019. Genzyme will have the option to development and commercialize these drugs outside of North America and Western Europe.

On the same day as the announcement of the new Alnylam/Genzyme deal, Alnylam acquired Merck’s RNAi program, which consists of what is left of the former  Sirna Therapeutics, for an upfront payment of $175 million in cash and stock. (This compares to the $1.1 billion that Merck paid for Sirna in 2006.) Alnylam will receive Merck’s RNAi intellectual property, certain preclinical drug candidates, and rights to Sirna/Merck’s RNAi delivery platform. Depending on the progress of any of Sirna/Merck’s products in development, Alnylam may also pay Merck up to $105 million in milestone payments per product.

Alnylam’s Phase 1 clinical studies with its ALN-TTR RNAi drugs

In August 2013, Alnylam and its collaborators published the results of their Phase 1 clinical trials of ALN-TTR01 and ALN-TTR02 (patisiran) in the New England Journal of Medicine. At the same time, Alnylam published a press release on this paper.

ALN-TTR01 and ALN-TTR02 contain exactly the same oligonucleotide molecule, which is designed to inhibit expression of the gene for TTR via RNA interference. They differ in that ALN-TTR01 is encapsulated in the first-generation version of liponanoparticle (LNP) carriers, and ALN-TTR02 is encapsulated in second-generation LNP carriers. Both types of LNP carriers are based on technology that is owned by Tekmira Pharmaceuticals (Vancouver, British Columbia, Canada) and licensed to Alnylam.

Tekmira’s LNP technology was formerly known as stable nucleic acid-lipid particle (SNALP) technology. Alnylam and Tekmira have had a longstanding history of collaboration involving SNALP/LNP technology, as described in our 2010 book-length report, RNAi Therapeutics: Second-Generation Candidates Build Momentum, published by Cambridge Healthtech Institute. Although the ownership of the intellectual property relating to SNALP/LNP technology had been the subject of litigation between the two companies, these disputes were settled in an agreement dated November 12, 2012. On December 16, 2013, Alnylam made a milestone payment of $5 million to Tekmira upon initiation of Phase 3 clinical trials of patisiran.

LNP-encapsulated oligonucleotides accumulate in the liver, which is the site of expression, synthesis, and secretion of TTR. As we discussed both in our book-length RNAi report, and in an article on this blog, delivery of oligonucleotide drugs (including “naked” oligonucleotides and LNP-encapsulated ones) to the liver is easier than targeting most other internal organs and tissues. The is a major reason for the emphasis on liver-targeting drugs by Alnylam and other therapeutic oligonucleotide companies.

To summarize the published report, each of the two formulations was studied in a single-dose, placebo-controlled Phase 1 trial. Both formulations showed rapid, dose-dependent, and durable RNAi-mediated reduction in blood TTR levels. (Both mutant and wild-type TTR production was suppressed by these drugs.)

ALN-TTR02 was much more potent than ALN-TTR01. Specifically, ALN-TTR01 at a dose of 1.0 milligram per kilogram, gave a mean reduction in TTR at day 7 of 38%, as compared with placebo. ALN-TTR02 gave mean reductions at doses from 0.15 to 0.3 milligrams per kilogram ranging from 82.3% to 86.8% at 7 days, with reductions of 56.6 to 67.1% at 28 days. The main adverse effects seen in the study were mild-to-moderate acute infusion reactions. These were observed in 20.8% of subjects receiving ALN-TTR01 and in 7.7% (one patient) of subjects receiving ALN-TTR02. These adverse effects could be managed by slowing the infusion rate. There were no significant increases in liver function test parameters in these studies.

The results of these studies have established proof-of-concept in humans that Alnylam’s TTR RNAi therapies can successfully target messenger RNA (mRNA) transcribed from the disease-causing gene for TTR. Alnylam also said in its press release that these results constitute “the most robust proof of concept for RNAi therapy in man to date”, and that they demonstrate proof-of-concept not only for RNAi therapeutics that target TTR, but also for therapeutic RNAi targeting of liver-expressed genes in general. They also note that this represents the first time that clinical results with an RNAi therapeutic have been published in the New England Journal of Medicine.

Other recent RNAi therapeutics deals, and the resurgence of the therapeutic RNAi field

The January 2014 Alnylam/Genzyme/Sanofi agreement is not the only therapeutic RNAi deal that has been making the news in 2013 and 2014. On July 31, 2013, Dicerna Pharmaceuticals (Watertown, MA) secured $60 million in an oversubscribed Series C venture financing. These monies will be used to conduct Phase 1 clinical trials of Dicerna’s experimental RNAi therapies for hepatocellular carcinoma and for unspecified genetically-defined targets in the liver. So far, Dicerna has raised a total of $110 million in venture capital.

Dicerna’s RNAi therapeutics are based on its proprietary Dicer substrate siRNA technology, and its EnCore lipid nanoparticle delivery vehicles.

On January 9, 2014, Santaris Pharma A/S (Hørsholm, Denmark) announced that it had signed a worldwide strategic alliance with Roche to discover and develop novel RNA-targeted medicines in several disease areas, using Santaris’ proprietary Locked Nucleic Acid (LNA) technology platform. Santaris will receive an upfront cash payment of $10 million, and a potential $138M in milestone payments. On January 10, 2014, Santaris announced another agreement to develop RNA-targeted medicines, this time with GlaxoSmithKline. Financial details of the agreement were not disclosed.

As in the case of Alnylam, we discussed Dicerna’s and Santaris’ technology platforms in our 2010 book-length report, RNAi Therapeutics: Second-Generation Candidates Build Momentum.

A January 15, 2014 FierceBiotech article reported that RNAi therapeutic deals were a hot topic at the 2014 J.P. Morgan Healthcare Conference in San Francisco, CA. This is a sign of the comeback of the therapeutic RNAi field, and of the return of interest by Big Pharma and by venture capitalists in RNAi drug development.


As the producers of this blog, and as consultants to the biotechnology and pharmaceutical industry, Haberman Associates would like to hear from you. If you are in a biotech or pharmaceutical company, and would like a 15-20-minute, no-obligation telephone discussion of issues raised by this or other blog articles, or of other issues that are important to  your company, please contact us by phone or e-mail. We also welcome your comments on this or any other article on this blog.

Can Merck’s R&D restructuring enable it to improve its productivity?

Simvastatin (Merck's Zocor)

Simvastatin (Merck’s Zocor)

On December 27th, 2013 the Wall Street Journal published an article by staff reporters Peter Loftus and Jonathan Rockoff about Merck’s new R&D restructuring. Fierce Biotech’s John Carroll also discussed the WSJ article in his own analysis dated December 28th, 2013.

According to these articles, Merck is in the process of cutting its internal R&D operations. This will include selling off dozens of pipeline compounds that have been under development in its labs. Merck also plans to cut its workforce by 20% over the next two years, as it had announced in October 2013. This will include reductions in its internal R&D staff.

At the same time, Merck will create new innovation hubs in Boston, the San Francisco Bay area, London and Shanghai.  The company has identified these geographic areas as having a critical mass of academic and commercial life science R&D. Merck intends to use its hubs as bases to scout for promising research that the company might license or acquire.

The overall plan is to reduce reliance on Merck’s internal R&D operations and to increase reliance on external R&D in academia and in biotech companies.

This is a similar strategy to that being followed by other Big Pharma companies, especially Johnson & Johnson and GlaxoSmithKline. All three of these companies are targeting some of the same geographic areas, especially Boston, California, London, and China.

Why are pharmaceutical companies struggling to develop new drugs?

The unveiling of Merck’s restructuring plans has triggered a wave of articles commenting on the wider implications of the move. David Shaywitz, M.D., Ph.D. (Director, Strategic and Commercial Planning at Theravance in South San Francisco, CA) writes in Forbes (12/29/2013) that pharma companies’ restructuring plans may save neither the companies carrying them out nor the pharmaceutical industry.

The reason that Merck and other pharma companies are carrying out these restructurings is that the companies are struggling to develop new drugs, and their internal labs are not producing them. The hope is that shifting from–as Dr. Shaywitz puts it–research and development to [external] search and development will produce more and better developable drugs. However, it may not do so. Outside partners may not necessarily know more about drug discovery than Merck Research Laboratories does.

The basic question then becomes why pharma companies are struggling to produce new products in the first place. One highly cited possibility is that Big Pharma companies are too bureaucratic, and thus inhibit their own ability to innovate. However, the underlying problem may well be that our understanding of biology–in health and disease–is limited.

The new President of Merck Research Laboratories, Roger M. Perlmutter, M.D., Ph.D. said, as quoted in another Forbes article:

“…if we’re discovering drugs, the problem is that we just don’t know enough. We really understand very little about human physiology. We don’t know how the machine works, so it’s not a surprise that when it’s broken, we don’t know how to fix it. The fact that we ever make a drug that gives favorable effects is a bloody miracle because it’s very difficult to understand what went wrong.”

Dr. Perlmutter then goes on to cite the example of statin drugs such as Merck’s Zocor (simvastatin) and Pfizer’s LIpitor (atorvastatin). Beginning in Merck’s own laboratories, under the company’s legendary R&D leader and CEO Roy Vagelos, statins were designed to lower blood cholesterol levels by inhibiting the enzyme HMG-CoA reductase. However, statins also appear to prevent atherosclerosis by a variety of other mechanisms (e.g., modulating inflammation). Thus their true mechanisms of action are not well understood.

How can companies carry out biology-driven R&D?

Despite the fact that our knowledge of biology is limited, we and others have noted that the most successful drug discovery and development strategy in the last two decades or so has been biology-driven R&D. For example, this is the basis of the entire R&D program of such companies as Novartis and Genentech. How is it possible to conduct reasonably successful biology-driven R&D if our knowledge of human biology is so limited?

We have discussed reasons for the success of biology-driven R&D in our book-length report Approaches to Reducing Phase II Attrition, and in our published article in Genetic Engineering and Biotechnology News “Overcoming Phase II Attrition Problem”.

Briefly, biology-driven drug discovery has often utilized academic research into pathways, disease models, and other biological systems, which have been conducted over a period of years or of decades. Targets and pathways derived from this research are usually relatively well understood and validated, with respect to their physiological functions and their roles in disease.  Examples of drugs derived from such research include most approved biologics (e.g., Genentech’s Herceptin and Biogen Idec/Genentech’s Rituxan), as well as the numerous protein kinase inhibitors for treatment of cancers. It was the successful development of the kinase inhibitor imatinib (Gleevec/Glivec) that led Novartis to adopt its pathway-based strategy in the first place.

A more recent example is the work on discovery and development of monoclonal antibody (MAb)-based immunotherapies for cancer, which we highlighted in our January 3, 2014 blog article on Science’s Breakthrough of the Year. These drugs include the approved CTLA4-targeting agent ipilimumab (Bristol-Myers Squibb’s Yervoy), and several other agents that target the PD-1/PD-L1 checkpoint pathway, including Merck’s own anti-PD-1 agent lambrolizumab.

The development of these agents was made possible by a line of academic research on T cells that was begun in the 1980s by James P Allison, Ph.D. Even after Dr. Allison’s research demonstrated in 1996 that an antibody that targeted CTLA-4 had anti-tumor activity in mice, no pharmaceutical company would agree to work on this system. However, the MAb specialist company Medarex licensed the antibody in 1999. Bristol-Myers Squibb acquired Medarex in 2009, and Yervoy was approved in 2011.

The above examples show that although we do not understand human physiology in health and decease in general, we do understand pieces of biology that are actionable for drug discovery and development. This understanding often comes after decades of effort. One strategy for a scout in a Big Pharma innovation hub might be to look for such actionable pieces of biology, and to contract with the academic lab or biotech company that developed them for licenses or partnerships. However, the case of Yervoy shows that pharmaceutical companies may not recognize these actionable areas, or may be slow to do so.

Moreover, for many diseases of great interest to physicians and patients, academic researchers, and/or companies, we may not have an actionable piece of biology that is backed by decades of research. We may only have interesting (and perhaps breakthrough) research that has been carried out over only a few years. In these cases (and even in cases based on deeper understand based on decades of research), companies will need to develop a set of “fail fast and fail cheaply” strategies. Such strategies usually reside in small biotechs rather than in Big Pharmas. Moreover, these strategies remain a work in progress.


As the producers of this blog, and as consultants to the biotechnology and pharmaceutical industry, Haberman Associates would like to hear from you. If you are in a biotech or pharmaceutical company, and would like a 15-20-minute, no-obligation telephone discussion of issues raised by this or other blog articles, or of other issues that are important to  your company, please contact us by phone or e-mail. We also welcome your comments on this or any other article on this blog.

Neuroscience companies sprout up in Boston

Pyramidal neurons. Source: Magnus Manske

Pyramidal neurons. Source: Magnus Manske

In our December 10, 2013 blog article that focused on Novartis’ new neuroscience division, we briefly mentioned two young Cambridge MA neuroscience specialty companies–Rodin Therapeutics and Sage Therapeutics.

Rodin Therapeutics

Rodin was founded by Atlas Venture and the German protein structure-focused biotech Proteros biostructures in June 2013. It is focused on applying epigenetics to discovery and development of novel therapeutics for CNS disorders, especially cognitive disorders such as Alzheimer’s disease. Rodin secured funding from Atlas and Johnson & Johnson Development Corporation (JJDC). The company plans to collaborate with the Johnson & Johnson Innovation Center in Boston and Janssen Research & Development to advance its R&D programs. In addition to several partners at Atlas (led by acting Rodin Chief Executive Officer Bruce Booth, Ph.D.), Rodin’s team includes as its Chief Scientific Officer Martin Jefson Ph.D., former head of Neuroscience Research at Pfizer.

There is little information available on Rodin, because the company is operating in stealth mode.

Sage Therapeutics

Sage was founded by venture capital firm Third Rock Ventures, and officially launched on October 2011. At the time of its launch, Third Rock provided Sage with a $35 million Series A round of financing. Third Rock founded Sage together with scientific founders Steven Paul, M.D. (formerly the Executive Vice President for science and technology and President of Lilly Research Laboratories, and a former scientific director of the National Institute of Mental Health) and Douglas Covey, Ph.D. (professor of biochemistry at the Washington University School of Medicine, St. Louis, MO).

We at Haberman Associates have known Dr. Paul mainly for his work in R&D strategy while at Lilly. We cited Dr. Paul in our 2009 book-length report, Approaches to Reducing Phase II Attrition, published by Cambridge Healthtech Institute.

In October 2013, Sage received $20 million in Series B financing from Third Rock and from ARCH Venture Partners.

Sage’s technology platform is based on targeting certain classes of neurotransmitter receptors. As we discussed in our December 10, 2013 blog article, targeting neurotransmitter receptors was a successful approach to drug discovery and development decades ago, but has proven nearly fruitless ever since.

Nevertheless, Sage is taking a novel and interesting approach to targeting neurotransmitter receptors. The company is focusing on receptors for gamma aminobutyric acid (GABA) and glutamate. GABA and glutamate are, respectively, the primary inhibitory and excitatory neurotransmitters that mediate fast synaptic transmission in the brain. Specifically, Sage is focusing on GABAreceptors (a major class of GABA receptors) and N-methyl-D-aspartic acid (NMDA) receptors (a major class of glutamate receptors).

Both GABAA receptors and NMDA receptors are ligand-gated ion channels. These multi-subunit proteins are transmembrane ion channels that open to allow ions such as Na+, K+, Ca2+, or Cl- to pass through the membrane in response to the binding of a ligand, such as a neurotransmitter. [In addition to ligand-gated ion channels, neurotransmitter receptors include members of the G-protein coupled receptor (GPCR) family. One example is the GABAB receptor.]

The GABAA receptor is a pentameric (five-subunit) chloride channel whose endogenous ligand is GABA. In addition to its binding site for GABA, this receptor has several allosteric sites that modulate its activity indirectly. Among the drugs that target an allosteric site on GABAA receptors are the benzodiazepines. Examples of benzodiazepines include the tranquilizer (anxiolytic) diazepam (Valium), and the short-term anti-insomnia drug Triazolam (Halcion).

The NMDA receptor is a heterotetrameric cation channel. It is a type of glutamate receptor. NMDA is a selective agonist that binds to NMDA receptors but not to other glutamate receptors. Calcium flux through NMDA receptors is thought to be critical for synaptic plasticity, a cellular mechanism involved in learning and memory. NMDA receptors require co-activation by two ligands: glutamate and either D-serine or glycine. (NMDA itself is a partial agonist that mimics glutamate, but is not normally found in the brain.) Among the drugs that act as NMDA receptor antagonists are the cough suppressant (antitussive) dextromethorphan and the Alzheimer’s drug memantine.

Imbalance in the levels of GABA and glutamate, or alterations in activity of their receptors can result in dysregulation of neural circuits. Such imbalance has been implicated in neuropsychiatric disorders such as epilepsy, autism, schizophrenia and pain. While GABAA receptors and NMDA receptors are considered to be validated drug targets, a major challenge has been to modulate these receptors safely and effectively. Current drugs that act at these receptors have major adverse effects (e.g., sedation, seizures, tolerance, dependence, and excitotoxicity) that strongly impair patient quality of life. For example, long-term treatment with benzodiazepines can cause tolerance and physical dependence, and dextromethorphan can act as a dissociative hallucinogen.

Sage’s proprietary technology platform is based on the identification of members of a family of small-molecule endogenous allosteric modulators, which selectively and potently modulate GABAA or NMDA receptors. Sage is developing proprietary derivatives of these compounds. The goal of Sage’s R&D is to discover and develop  positive and negative allosteric modulators of GABAA and NMDA receptors that can be used to restore the balance between GABA and glutamate receptor activity that is disrupted in several important CNS disorders. These compounds will be designed to “fine tune” GABAA and NMDA receptor activity, resulting in a greater degree of both efficacy and safety than current CNS therapeutics.

For example, in October 2013, Sage announced the publication of a research report in the October 30, 2013 issue of the Journal of Neuroscience. The report detailed the results of research at Sage, on the identification of an endogenous brain neurosteroid, the cholesterol metabolite 24(S)-hydroxycholesterol (24(S)-HC).  This compound is a potent (submicromolar), direct, and selective positive allosteric regulator of NMDA receptors. The researchers found that 24(S)-HC binds to a modulatory allosteric site that is unique to oxysterols. Subsequent drug discovery efforts resulted in the identification of several potent synthetic drug-like derivatives of 24(S)-HC that act as the same allosteric site, and serve as positive modulators of NMDA receptors. Treatment with one of these derivatives, Sage’s propriety compound SGE-301, reversed behavioral and cognitive deficits in a variety of preclinical models.

Sage’s pipeline

Sage has four pipeline drug candidates, including two compounds in the clinic. The company says that its initial pipeline focus is on “acute and orphan CNS indications with strong preclinical to clinical translation and accelerated development timelines” that enable the rapid development of important therapeutics to treat these conditions. In addition, Sage is pursuing early-stage programs that utilize the company’s PANAM platform. The goal of the early-stage programs (which target GABAA and NMDA receptors as we discussed earlier in this article) is to address “prevalent, chronic neuropsychiatric indications.”

Sage’s pipeline drug candidates include compounds in Phase 2 trials to treat status epilepticus and traumatic brain injury, and two preclinical-stage compounds–an anesthetic a treatment for patients with fragile X syndrome.

Status epilepticus (SE) is an acute life-threatening form of epilepsy, which is currently defined as a continuous seizure lasting longer than 5 minutes, or recurrent seizures without regaining consciousness between seizures for over 5 minutes. It occurs in approximately 200,000 U.S. patients each year, and has a mortality rate of nearly 20%. Refractory SE occurs in around a third of SE patients for whom first and second line treatment options are ineffective. These patients are moved to the ICU, and have little or no treatment options.

Sage’s SAGE-547, which is a proprietary positive GABAA receptor allosteric modulator, is aimed at treatment of the orphan indication of refractory SE. This compound has been selected by Elsevier Business Intelligence as one of the Top 10 Neuroscience Projects to Watch.

In addition to SAGE-547, Sage is developing next-generation treatments for SE and other forms of seizure and epilepsy. These early-stage compounds are novel positive allosteric modulators of GABAA receptors. Sage presented data on its early-stage therapeutics for SE in a poster session at the American Epilepsy Society (AES) Annual Meeting, Cambridge MA, December 9, 2013.

Sage’s drug candidate for traumatic brain injury is listed on the company’s website as “a proprietary, positive allosteric modulator”.

Sage’s preclinical anesthetic, SGE-202, is moving toward a Phase 1 clinical trial in 2014. It is an intravenous anesthetic for procedural sedation that designed to compete with the standard therapy, propofol. SGE-202 is designed to offer improved efficacy and safety as compared to propofol.

Fragile X syndrome (FSX) is an X chromosome-linked genetic syndrome that is the most widespread monogenic cause of autism and inherited cause of intellectual disability in males. FSX is an orphan condition that affects 60,000 – 80,000 people in the U.S. It causes such impairments as anxiety and social phobia, as well as cognitive deficits. There are no currently approved therapies for FXS, but patients are often prescribed treatments for anxiety, attention deficit hyperactivity disorder (ADHD) and/or epilepsy.

Sage is developing a proprietary positive GABAA receptor allosteric modulator for treatment of FSX. It is expected to provide symptomatic and potentially disease-modifying therapeutic benefits to patients with FXS, and to ameliorate anxiety and social deficits. The company is moving its FXS program toward a Phase 1 clinical trial in 2014.

EnVivo Pharmaceuticals

Sage is not the only Boston-area biotech that is developing novel classes of compounds to target specific types of neurotransmitter receptors. We discussed EnVivo Pharmaceuticals (Watertown, MA), and its program to develop agents to target subclasses of nicotinic acetylcholine receptors (nAChRs), in a November 2007 report published by Decision Resources.

nAChRs, like GABAA and NMDA receptors, are ligand-gated ion channels. In normal physiology, nAChRs are opened by the neurotransmitter acetylcholine (ACh). However, nicotine can also open these receptors. Certain subtypes of nAChRs in the brain are involved in cognitive function, and nicotine, by targeting these receptors, has long been known to improve cognitive function. However, the adverse effects of nicotine (especially its well-known addictive properties) make this drug problematic for use as a cognitive enhancer. Therefore, several companies have been working on discovering and developing subtype-specific nAChR agonists for use in such conditions as Alzheimer’s disease, schizophrenia, ADHD, and mild cognitive impairment.

EnVivo’s alpha-7 nAChR program, which targets a subtype of nChRs that have been implicated in cognitive function, has made considerable progress since 2007. Their lead compound, EVP-6124, is now in Phase 3 clinical trials for treatment of schizophrenia, and Phase 3 trials in Alzheimer’s disease are planned. This follows positive Phase 2 results in both conditions.


Sage Therapeutics has a sophisticated approach to discovery of compounds that modulate GABAA and NMDA receptors, and has managed to both attract significant venture financing and to move compounds into the clinic rapidly. However, none of Sage’s compounds has yet achieved clinical proof of concept, so it is too early to determine whether Sage’s approach will bear fruit.

EnVivo’s alpha-7 nAChR program is based on a more straightforward technology strategy than Sage’s. It has made considerable progress since we first covered it in 2007. EnVivo’s lead compound, EVP-6124, has had successful Phase 2 clinical trials in both Alzheimer’s disease and schizophrenia. However, both of these diseases have proven very difficult for drug developers to tackle. This is particularly true for Alzheimer’s disease–we have covered several cases in which drugs failed in Phase 3 on this blog. Therefore, it is best to reserve judgment on the outlook for EnVivo’s alpha-7 nAChR program pending the results of the Phase 3 trials.

Moreover, as we discussed on this blog, many Alzheimer’s experts believe that it would be best to target very early-stage or pre-Alzheimer’s disease rather than even “mild-to-moderate” disease as in the EnVivo Phase 2 trials.

Novartis’ new neuroscience program is a foundational, early-stage biology-driven effort, and clinical compounds are not expected for five years or so. Therefore, if Sage’s and especially EnVivo’s programs bear fruit, we should know about it long before any Novartis CNS programs progress very far at all. However, it is because of the abject failure of neurotransmitter-targeting approaches to CNS drug discovery and development over several decades that Novartis is resorting to a long-term foundational CNS R&D strategy.


As the producers of this blog, and as consultants to the biotechnology and pharmaceutical industry, Haberman Associates would like to hear from you. If you are in a biotech or pharmaceutical company, and would like a 15-20-minute, no-obligation telephone discussion of issues raised by this or other blog articles, or of other issues that are important to  your company, please contact us by phone or e-mail. We also welcome your comments on this or any other article on this blog.

Will Novartis lead a pharma industry return to neuroscience R&D?

Pyramidal neurons. Source: Retama.

Pyramidal neurons. Source: Retama.

A prominent feature of pharmaceutical company strategy in recent years has been massive cuts in R&D. These cutbacks have hit especially hard in areas that have not been productive in terms of revenue-producing drugs.

Chief among the targets for R&D cuts and layoffs has been neuroscience. As outlined in a 2011 Wall Street Journal article, such companies as AstraZeneca, GlaxoSmithKline, Sanofi, and Merck have cut back on neuroscience R&D, especially in psychiatric diseases. (Neurodegenerative diseases such as Alzheimer’s, despite the frustrations of working in this area, have continued to hold some companies’ interest.)

The retreat from psychiatric disease R&D has been occurring despite the fact that mental health disorders are the most costly diseases in Western countries. For example, according to the same Wall Street Journal article, mental disorders were number one in the European Union in terms of direct and indirect health costs in recent years. In 2007, the total cost of these conditions in Europe was estimated at €295 billion ($415 billion). Indirect costs, especially lost productivity, accounted for most of these costs.

The Novartis return to neuroscience R&D

Now comes a Nature News article by Alison Abbott, Ph.D. (Nature’s Senior European Correspondent in Munich)–dated 08 October 2013, entitled “Novartis reboots brain division”.

As discussed in that article, Novartis closed its neuroscience facility at its headquarters in Basel, Switzerland in 2012. However, as was planned at the time of this closure, Novartis is now starting a new neuroscience research program at its global R&D headquarters, the Novartis Institutes for BioMedical Research (NIBR) (Cambridge, MA).

The old facility’s research was based on conventional approaches, centered on the modulation of neurotransmitters. This approach had been successful in the 1960s and 1970s, especially at Novartis’ predecessor companies. In that era, Sandoz developed clozapine, the first of the so-called “atypical antipsychotic” drugs, and Ciba developed imipramine, the first tricyclic antidepressant.

Since the development of these and other then-breakthrough psychiatric drugs, the market has become inundated with cheap generic antidepressants, antipsychotics and other psychiatric drugs. These drugs act on well-known targets–mainly neurotransmitter receptors.

Neurotransmitter receptor-based R&D has become increasingly ineffective. What has been needed are new paradigms of R&D strategy to address the lack of actionable knowledge of CNS biology. As a result of this knowledge deficit, pharmaceutical industry CNS research has become increasingly ineffective, which is the motivation for the cutbacks and layoffs in this area. Moreover, there have been no substantial improvements in therapy. For example, there are no disease-modifying drugs for autism, or for the cognitive deficits of schizophrenia.

Novartis’ return to neuroscience is based on a fresh approach to R&D strategy, based on exciting developments in academic neurobiology. This strategy is based on study of such areas as:

  • Neural circuitry, and how it may malfunction in psychiatric disease
  • The genetics of psychiatric diseases
  • The technology of optogenetics, which enables researchers to identify the neural circuits that genes involved in psychiatric disorders affect.
  • The use of induced pluripotent stem cell (iPS) technology, which enables researchers to take skin cells from patients, induce them to pluripotency, differentiate the iPS cells into neurons, and study aspects of their cell biology that may contribute to disease.

In support of this strategy, Novartis has hired an academic, Ricardo Dolmetsch, Ph.D. (Stanford University) to lead its new neuroscience division. Dr. Dolmetsch’s research has focused on the neurobiology of autism and other neurodevelopmental disorders. His laboratory has been especially interested in how electrical activity and calcium signals control brain development, and how this may be altered in children with autism spectrum disorders (ASDs).

The projects in the Dolmetsch laboratory have included:

  • Use of iPS technology–as well as mouse and Drosophila models–to study the underlying basis of ASDs.
  • Studies of calcium channels and calcium signaling in neurons, their role in development, and how they may be altered in neural diseases.
  • The development of new technologies to study neural development, and developing new pharmaceuticals that regulate calcium channels and that may be useful for treating ASDs and other diseases.

Novartis’ new approach to neuroscience is completely consistent with the company’s overall biology-driven (and more specifically pathway-driven) approach to drug discovery and development. We discussed this strategy in our July 20, 2009 article on the Biopharmconsortium Blog. We also discussed more recent development with Novartis’ overall strategy in our September 4, 2013 article on this blog.

Interestingly, the idea of hiring an academic to head Novartis’ new neuroscience division replicates the hiring of an academic–Mark Fishman, M.D. (formerly at the Massachusetts General Hospital, Harvard Medical School, Boston MA)–as the overall head of the Novartis Institutes for BioMedical Research in 2002.

Novartis’ timeline for neuroscience drug development

Novartis neuroscience program intends to work toward discovery and development of therapeutics for such neurodevelopmental conditions as ASD, schizophrenia and bipolar disorder, as well as for neurodegenerative diseases such as Parkinson’s and Alzheimer’s diseases.

All of the technologies and research strategies that Novartis plans to use in its neuroscience division are novel ones, and mainly reside in academic laboratories. Novartis therefore plans to collaborate with academia in its neuroscience research efforts–as it does in other areas.

The collaboration between Novartis and academic labs will be facilitated by accepting the norms of academic research. Research results will be published, and academic institutions will be allowed to patent targets and technologies that emerge from the research. However, Novartis will have the right to develop drugs based on the targets, and will have the right of first refusal to license the patents.

According to Dr. Dolmetsch, and to Novartis advisor Steven E. Hyman, M.D (director of the Stanley Center for Psychiatric Research at the Broad Institute, Cambridge, MA), Novartis’ new approach to neuroscience will take a long time (perhaps around 5 years) before the first drugs start entering the clinic. As with other project areas  based on Novartis’ pathway-driven drug discovery strategy, it is likely that the first clinical studies will be in rare diseases (e.g., types of autism driven by specific genetic determinants).

Is Novartis leading the way to a broader industry return to neuroscience?

An important question is whether other pharmaceutical and biotechnology companies will follow Novartis into a return to neuroscience R&D, based on biology-driven strategies. According to Alison Abbott’s article, Roche is planning such a program. However, other Big Pharmas are so far staying out.

Meanwhile, the European Commission, via its Innovative Medicines Initiative, is attempting to foster academic/pharma industry collaboration to study genetics and neural circuitry in autism, schizophrenia and depression. In the United States, the National Institutes of Health has launched the Brain Research through Advancing Innovative Neurotechnologies (BRAIN) Initiative, focused on study of neural circuitry.

Entrepreneurial start-up biotech companies, backed by leading venture capitalists, have also been exploring novel neuroscience-based approaches to drug discovery and development. For example, in Cambridge MA, there are Sage Therapeutics (backed by Third Rock Ventures and ARCH Ventures), and Rodin Therapeutics (backed by Atlas Venture). However, another Cambridge MA neuroscience company, Satori Pharmaceuticals, which had been focused on Alzheimer’s, had to close its doors in May 30, 2013, after the preclinical safety failure of its lead compound. This illustrates the risky nature of neuroscience-based drug development, especially in small biotech companies.

Nevertheless, after the decades-long failure of neurotransmitter receptor-based R&D to yield breakthrough drugs for devastating psychiatric and neurodegenerative diseases, biology-driven drug discovery R&D appears to be the way to go.


As the producers of this blog, and as consultants to the biotechnology and pharmaceutical industry, Haberman Associates would like to hear from you. If you are in a biotech or pharmaceutical company, and would like a 15-20-minute, no-obligation telephone discussion of issues raised by this or other blog articles, or of other issues that are important to  your company, please contact us by phone or e-mail. We also welcome your comments on this or any other article on this blog.

Agios Pharmaceuticals becomes a clinical-stage company!

Agios Efstratios, Greece. Source: Christef

Agios Efstratios, Greece. Source: Christef

In a news release on September 23, 2013, Agios Pharmaceuticals (Cambridge, MA) announced that it had initiated its first clinical study. The company further discussed its early clinical and preclinical programs in its press release on its Third Quarter financial report, dated November 7, 2013.

Specifically, the company initiated a Phase 1 muticenter clinical trial of AG-221 in patients with advanced hematologic malignancies bearing an isocitrate dehydrogenase 2 (IDH2) mutation. The study is designed to evaluate the safety, pharmacokinetics, pharmacodynamics and efficacy of orally-administered AG-221 in this patient population. The first stage of the Phase 1 study is a dose-escalation phase, which is designed  to determine the maximum tolerated dose and/or the recommended dose to be used in Phase 2 studies. After the completion of this phase, several cohorts of patients will receive AG-221 to further evaluate the safety, tolerability and clinical activity of the maximum tolerated dose.

We discussed AG-221 in our June 17, 2013 article on this blog. AG-221 is an orally available, selective, potent inhibitor of the mutated IDH2 protein. It is thus a targeted (and personalized) therapy for patients with cancers with an IDH2 mutation.

As we summarized in our June 17, 2013 article, wild-type IDH1 and IDH2 catalyze the NADP+-dependent oxidative decarboxylation of isocitrate to α-ketoglutarate. Mutant forms of IDH1 and IDH2, which are found in certain human cancers, no longer catalyze this reaction, but instead catalyzes the NADPH-dependent reduction of α-ketoglutarate to R(-)-2-hydroxyglutarate (2-HG). Agios researchers hypothesized that 2HG is an oncometabolite. They further hypothesized that developing mutant-specific small molecule inhibitors of IDH1 and IDH2 might inhibit the growth or reverse the oncogenic phenotype of cancer cells that carry the mutant enzymes.

As we further discussed in our article, Agios researchers published two articles in the journal Science in May 2013 that support these hypotheses. The researchers showed that drugs that inhibit the mutant forms of IDH1 and IDH2 can reverse the oncogenic effects of the mutant enzymes in patient-derived tumor samples. These results constitute preclinical support for the hypothesis that the two mutant enzymes are driving disease, and that drugs that target the mutant forms of the enzymes can reverse their oncogenic effects.

In the results reported in one of these research articles, Agios researchers tested a mutant-IDH2 inhibitor in hematologic malignancies (including one model leukemia and one patient-derived leukemia), and showed that treatment with the inhibitor caused differentiation of the leukemic cells to normal blood cells. This preclinical study thus supports the initiation of Agios’ new Phase 1 study of AG-221 in patients with mutant-IDH2 bearing hematologic malignancies.

Additional pipeline news in Agios’ Third Quarter 2013 Report

In addition to the report of the initiation of Phase 1 studies of AG-221, Agios reported  that it had advanced AG-120, a mutant-IDH1 inhibitor, toward Investigational New Drug (IND) filing. The company plans to initiate Phase 1 clinical trials of AG-120 in early 2014, in  patients with advanced solid and hematological malignancies that carry an IDH1 mutation.

Agios also reported in their Third Quarter 2013 Report that the company had advanced AG-348 into IND-enabling studies. AG-348 is an activator of pyruvate kinase R (PKR). Germline mutation of PKR can result in pyruvate kinase deficiency (PK deficiency), a form of familial hemolytic anemia. Agios’ in vitro studies indicate that PKR activators can enhance the activity of most common PKR mutations, and suggest that these compounds may be potential treatments for PK deficiency.

Agios’ AG-348 program is part of its R&D aimed at development of treatments for inborn errors of metabolism (IEM). We discussed this program in our November 30, 2011 article on this blog.

Agios to present preclinical research at the ASH meeting in December 2013

In a second November 7, 2013 press release, Agios announced that it would present the results of the preclinical studies of its lead programs in cancer metabolism and in IEM at the 2013 American Society of Hematology (ASH) Annual Meeting, December 7-10, 2013 in New Orleans, LA.

Agios researchers will give one presentation on a study of AG-221 treatment in a primary human IDH2 mutant bearing acute myeloid leukemia (AML) xenograft model. They will also present two posters–one on a mutant-IDH1 inhibitor in combination with Ara-C (arabinofuranosyl cytidine) in a primary human IDH1 mutant bearing AML xenograft model, and another on the effects of a small molecule activation of pyruvate kinase on metabolic activity in red cells from patients with pyruvate kinase deficiency-associated hemolytic anemia.

Can Agios Pharmaceuticals become a new Genentech?

On October 13, 2013, XConomy published an article on Agios’ CEO, David Schenkein. The article is entitled “David Schenkein, Cancer Doc Turned CEO, Aims to Build New Genentech”.

As many industry experts point out, the business environment is much different from that in which Genentech (and Amgen, Genzyme and Biogen) were founded, and grew to become major companies. As one illustration of the difference between the two eras, neither Genentech nor Genzyme are independent companies today. Biogen exists as a merged company, Biogen Idec, which between 2007 and 2011 had to fend off attacks by shareholder activist Carl Icahn.

Moreover, this has been the era of the “virtual biotech company”. These are lean companies with only a very few employees that outsource most of their functions, and that are designed to be acquired by a Big Pharma or large biotech company. The virtual company strategy has been designed to deal with the inability of most young biotech companies to go public in the current financial environment. (However, there has been a surge in biotech IPOs in the past year, including Agios’ own IPO on June 11, 2013. So it is possible that the environment for young biotech companies going public is changing.)

Nevertheless, the XConomy article states that when Dr. Schenkein was in discussions with venture capitalist Third Rock on becoming the CEO of one of their portfolio companies, he stated that he wanted “a company with a vision, and investor support, to be a long-term, independent company”. As we have discussed in this blog, and also in an interview for Chemical & Engineering News (C&EN), Agios’ strategy is to build a company that can endure as an independent firm over a long period of time, and that can also demonstrate sustained performance. This strategy has been characterized (especially in the 1990s and early 2000s) as “Built to Last”, a term that I used in the interview.

Later, Agios posted a reprint of the C&EN article on its website, which it retitled “Built to Last”. This illustrates Agios’ commitment to “Built to Last”, as is more importantly shown by the company’s financial and R&D strategy.

Even if Agios cannot become the next Genentech, it–as well as a few other young platform companies mentioned in the CE&N article–might become an important biotech or pharmaceutical company like Vertex. However, all depends on the success of Agios’ products in the clinic and at regulatory agencies like the FDA, as well as the future shape of the corporate, financial and health care environment.


As the producers of this blog, and as consultants to the biotechnology and pharmaceutical industry, Haberman Associates would like to hear from you. If you are in a biotech or pharmaceutical company, and would like a 15-20-minute, no-obligation telephone discussion of issues raised by this or other blog articles, or an initial one-to-one consultation on an issue that is key to your company’s success, please contact us by phone or e-mail. We also welcome your comments on this or any other article on this blog.

Chemokine receptor inhibitors for prevention of cancer metastasis

CXCR-1 N-terminal peptide bound to IL-8

CXCR-1 N-terminal peptide bound to IL-8

In our October 31, 2013 blog article, we discussed recent structural studies of the chemokine receptors CCR5 and CXCR4. We discussed the implications of these studies for the treatment of HIV/AIDS, especially using the CCR5 inhibitor maraviroc (Pfizer’s Selzentry/Celsentri). As discussed in the article, researchers are utilizing the structural studies of CCR5 and CXCR4 to develop improved HIV entry inhibitors that target these chemokine receptors.

Meanwhile, other researchers have been studying the role of chemokine receptors in cancer biology, and the potential use of chemokine receptor antagonists in cancer treatment.

CCR5 antagonists as potential treatments for metastatic breast cancer

One group of researchers, led by Richard G. Pestell, M.D., Ph.D. (Thomas Jefferson University, Philadelphia, PA) has been studying expression of CCR5 and its ligand CCL5 (also known as RANTES) and their role in breast cancer biology and pathogenesis. Their report of this study was published in the August 1, 2012 issue of Cancer Research.

These researchers first studied the combined expression of CCL5 and CCR5 in various subtypes of breast cancer, by analyzing a microarray database of over 2,000 human breast cancer samples. (The database was compiled from 27 independent studies). They found that CCL5/CCR5 expression was preferentially expressed in the basal and HER-2 positive subpopulations of human breast cancer.

Because of the high level of unmet medical need in treatment of basal breast cancer, the authors chose to focus their study on this breast cancer subtype. As the researchers point out, patients with basal breast cancer have increased risk of metastasis and low survival rates. Basal tumors in most cases do not express either androgen receptors, estrogen receptors (ERs), or HER-2. They thus cannot be treated with such standard receptor-targeting breast cancer therapeutics as tamoxifen, aromatase inhibitors, or trastuzumab. The only treatment options are cytotoxic chemotherapy, radiation, and/or surgery. However, these treatments typically results in early relapse and metastasis.

The basal breast cancer subpopulation shows a high degree of overlap with triple-negative (TN) breast cancer. We discussed TN breast cancer, and research aimed at defining subtypes and driver signaling pathways, in our August 2, 2011 article on this blog. In that article, we noted that TN breast cancers include two basal-like subtypes, at least according to one study. Other researchers found that 71% of TN breast cancers are of basal-like subtype, and that 77% of basal-like tumors are TN. A good part of the problem is that there is no accepted definition of basal-like breast cancers, and how best to define such tumors is controversial. However, both the TN and the basal subpopulations are very difficult to treat and have poor prognoses. It is thus crucial to find novel treatment strategies for these subpopulations of breast cancer.

Dr. Pestell and his colleagues therefore investigated the role of CCL5/CCR5 signaling in three human basal breast cancer cell lines that express CCR5. They found that CCL5 promoted intracellular calcium (Ca2+) signaling in these cells. The researchers then determined the effects of CCL5/CCR5 signaling in promoting in vitro cell invasion in a 3-dimensional invasion assay. For this assay, the researchers assessed the ability of cells to move from the bottom well of a Transwell chamber, across a membrane and through a collagen plug, in response to CCL5 as a chemoattractant. The researchers found that CCR5-positive cells, but not CCR5-negative cells, showed CCL5-dependent invasion.

The researchers then studied the ability of CCR5 inhibitors to block calcium signaling and in vitro invasion. The agents that they investigated were maraviroc and vicriviroc. Maraviroc (Pfizer’s Selzentry/Celsentri) is the marketed HIV-1 entry inhibitor that we discussed in our October 31, 2013 articleVicriviroc is an experimental HIV-1 inhibitor originally developed by Schering-Plough. Schering-Plough was acquired by Merck in 2009. Merck discontinued development of vicriviroc because the drug failed to meet primary efficacy endpoints in late stage trials.

Pestell et al. found that maraviroc and vicriviroc inhibited calcium responses by 65% and 90%, respectively in one of their CCR5-positive basal cell breast cancer lines, and gave similar results in another cell line. The researchers then found that  in two different CCR5-positive basal breast cancer cell lines, both maraviroc and vicriviroc inhibited in vitro invasion.

The researchers then studied the effect of maraviroc in blocking in vivo metastasis of a CCR5-positive basal cell breast cancer line, which had been genetically labeled with a fluorescent marker to facilitate noninvasive visualization by in vivo bioluminescence imaging (BLI). They used a standard in vivo lung metastasis assay, in which cells were injected into the tail veins of immunodeficient mice, and mice were treated by oral administration with either maraviroc or vehicle. The researchers then looked for lung metastases. They found that maraviroc-treated mice showed a significant reduction in both the number and the size of lung metastases, as compared to vehicle-treated mice.

In both in vitro and in vivo studies, the researchers showed that maraviroc did not affect cell viability or proliferation. In mice with established lung metastases, maraviroc did not affect tumor growth. Maraviroc inhibits only metastasis and homing of CCR5-positive basal cell breast cancer cells, but not their viability or proliferation.

As the result of their study, the researchers propose that CCR5 antagonists such as maraviroc and vicriviroc may be useful as adjuvant antimetastatic therapies for breast basal tumors with CCR5 overexpression.  They may also be useful as adjuvant antimetastatic treatments for other tumor types where CCR5 promotes metastasis, such as prostate and gastric cancer.

As usual, it must be emphasized that although this study is promising, it is only a preclinical proof-of-principle study in mice, which must be confirmed by human clinical trials.

In an October 25, 2013 Reuters news story, it was revealed that Citi analysts believe that Merck will take vicriviroc into the clinic  in cancer patients in 2014. Citi said that it expected vicriviroc to be tested in combination with “a Merck cancer immunotherapy” across multiple cancer types, including melanoma, colorectal, breast, prostate and liver cancer. (We discussed Merck’s promising cancer immunotherapy agent lambrolizumab/MK-3475 in our June 25, 2013 blog article. But the Merck agent to be tested together with vicriviroc was not disclosed in the Reuters news story.)

Despite this news story, Merck said that it had not disclosed any plans for clinical trials of vicriviroc in cancer.

The CXCR1 antagonist reparixin as a potential treatment for breast cancer

In our In April 2012 book-length report, “Advances in the Discovery of Protein-Protein Interaction Modulators” (published by Informa’s Scrip Insights), we discussed the case of the allosteric chemokine receptor antagonist reparixin (formerly known as repertaxin). Reparixin has been under developed by Dompé Farmaceutici (Milan, Italy). This agent targets both CXCR1 and CXCR2, which are receptors for interleukin-8 (IL-8). IL-8 is a well-known proinflammatory chemokine that is a major mediator of inflammation. As we discussed in our report, reparixin had been in Phase 2 development for the prevention of primary graft dysfunction after lung and kidney transplantation. However, it failed in clinical trials.

Meanwhile, researchers at the University of Michigan (led by Max S. Wicha, M.D., the Director of the University of Michigan Comprehensive Cancer Center) and at the Institut National de la Santé et de la Recherche Médicale (INSERM) in France were working to define a breast cancer stem cell signature using gene expression profiling. They found that CXCR1 was among the genes almost exclusively expressed in breast cancer stem cells, as compared with its expression in the bulk tumor.

IL-8 promoted invasion by the cancer stem cells, as demonstrated in an in vitro invasion assay. The CXCR1-positive, IL-8 sensitive cancer stem cell population was also found to give rise to many more metastases in mice than non-stem cell breast tumor cells isolate from the same cell line. This suggested the hypothesis that a CXCR1 inhibitor such as reparixin might be used as an anti-stem cell, antimetastatic agent in the treatment of breast cancer.

Dr. Wicha and his colleagues then studied the effects of blockade of CXCR1 by either reparixin or a CXCR1-specific blocking antibody on  bulk tumor and cancer stem cells in two breast cancer cell lines. The researchers found in in vitro studies that treatment with either of these two CXCR1 antagonists selectively depleted the cell lines of cancer stem cells (which represented 2% of the tumor cell population in both cell lines).

This depletion was followed by the induction of massive apoptosis of the bulk, non-stem tumor cells. This was mediated via a bystander effect, in which CXCR1-inhibited stem cells produce the soluble death mediator FASL (FAS ligand). FASL binds to FAS receptors on the bulk tumor cells, and induces an apoptotic pathway in these cells that results in their death.

In in vivo breast cancer xenograft models, the researchers treated tumor-bearing mice with either the cytotoxic agent docetaxel, reparixin, or a combination of both agents. Docetaxel treatment–with or without reparixin–resulted in a significant inhibition of tumor growth, while reparixin alone gave only a modest reduction in tumor growth. However, treatment with docetaxel alone gave no reduction (or an increase) in the percentage of stem cells in the tumors, while reparixin–either alone or in combination with docetaxel–gave a 75% reduction in the percentage of cancer stem cells. Moreover, in in vivo metastasis studies in mice, reparixin treatment gave a major reduction in systemic metastases. These results suggest that reparixin may be useful in eliminating breast cancer stem cells and in inhibiting metastasis and thus preventing recurrence of cancer in patients treated with chemotherapy.

As we discussed in our 2012 report, Dr. Wicha’s research on reperixin might represent an opportunity for Dompé to repurpose reperixin for cancer treatment. Since the publication of the 2012 report, Dompé has been carrying out a Phase 2 pilot study of reparixin in patients diagnosed with early, operable breast cancer, prior to their treatment via surgery. The goal of this study is to investigate if cancer stem cells decrease in two early breast cancer subgroups (estrogen receptor-positive and/or progesterone receptor positive/HER-2-negative, and estrogen receptor negative/progesterone receptor negative/HER-2-negative). The goal is to compare any differences between the two subgroups in order to better identify a target population.

Dompé has thus begun the process of clinical evaluation of reparixin for the new indication–treatment of breast cancer in order to inhibit metastasis and prevent recurrence.


Researchers have found promising evidence that at least two chemokine/chemokine receptor combinations may be involved in cancer stem cell biology and thus in the processes of metastasis and cancer recurrence. In at least one case–and perhaps both–companies are in the early stages of developing small-molecule chemokine receptor antagonists for inhibiting breast cancer metastasis and recurrence. Such a strategy might be applicable to other types of cancer as well.

As discussed by Wicha et al., in immune and inflammatory processes, chemokines serve to facilitate the homing and migration of immune cells. In the case of cancer, chemokines may act as “stemokines”, by facilitating the homing of cancer stem cells in the process of metastasis. Other chemokines and their receptors than those discussed in this article may be involved in other types of cancer, and may carry out similar “stemokine” functions.

Since around 90% of cancer deaths are due to metastasis, and since effective treatments for metastatic cancers are few, this is a potentially important area of cancer research and drug development.


As the producers of this blog, and as consultants to the biotechnology and pharmaceutical industry, Haberman Associates would like to hear from you. If you are in a biotech or pharmaceutical company, and would like a 15-20-minute, no-obligation telephone discussion of issues raised by this or other blog articles, or of other issues that are important to  your company,  please contact us by phone or e-mail. We also welcome your comments on this or any other article on this blog.

Chemokine receptors and the HIV-1 entry inhibitor maraviroc



In April 2012, Informa’s Scrip Insights published our book-length report, “Advances in the Discovery of Protein-Protein Interaction Modulators.” We also published a brief introduction to this report, highlighting the strategic importance of protein-protein interaction (PPI) modulators for the pharmaceutical industry, on the Biopharmconsortium Blog.

The report included a discussion on discovery and development of inhibitors of chemokine receptors. Chemokine receptors are members of the G-protein coupled receptor (GPCR) superfamily. GPCRs are seven-transmembrane (7TM) domain receptors (i.e. integral membrane proteins that have seven membrane-spanning domains). Compounds that target GPCRs represent the largest class of drugs produced by the pharmaceutical industry. However, in the vast majority of cases, these compounds target GPCRs that bind to natural small-molecule ligands.

Chemokine receptors, however, bind to small proteins, the chemokines. These proteins constitute a class of small cytokines that guide the migration of immune cells via chemotaxis. Chemokine receptors are thus a class of GPCRs that function by forming PPIs. Direct targeting of interactions between chemokines and their receptors (unlike targeting the interactions between small-molecule GPCR ligands and their receptors) thus involves all the difficulties of targeting other types of PPIs.

However, GPCRs–including chemokine receptors–appear to be especially susceptible to targeting via allosteric modulators. Allosteric sites lie outside the binding site for the protein’s natural ligand. However, modulators that bind to allosteric sites change the conformation of the protein in such a way that it affects the activity of the ligand binding site. (Direct GPCR modulators that bind to the same site as the GPCR’s natural ligands are known as orthosteric modulators.) In the case of chemokine receptors, researchers can in some cases discover small-molecule allosteric modulators that activate or inhibit binding of the receptor to its natural ligands. Discovery of such allosteric activators is much easier than discovery of direct PPI modulators.

Chemokines bind to sites that are located in the extracellular domains of their receptors. Allosteric sites on chemokine receptors, however, are typically located in transmembrane domains that are distinct from the chemokine binding sites. Small-molecule allosteric modulators that bind to these sites were discovered via fairly standard medicinal chemistry and high-throughput screening, sometimes augmented with structure-based drug design. This is in contrast to attempts to discover small molecule agents that directly inhibit binding of a chemokine to its receptor, which has so far been extremely challenging.

Our report describes several allosteric chemokine receptor modulators that are in clinical development, as well as the two agents that have reached the market. One of the marketed agents, plerixafor (AMD3100) (Genzyme’s Mozobil), is an inhibitor of the chemokine receptor CXCR4. It is used in combination with granulocyte colony-stimulating factor (G-CSF) to mobilize hematopoietic stem cells to the peripheral blood for autologous transplantation in patients with non-Hodgkin lymphoma and multiple myeloma. The other agent, which is the focus of this blog post, is maraviroc (Pfizer’s Selzentry/Celsentri).

Maraviroc is a human immunodeficiency virus-1 (HIV-1) entry inhibitor. This compound is an antagonist of the CCR5 chemokine receptor. CCR5 is specific for the chemokines RANTES (Regulated on Activation, Normal T Expressed and Secreted) and macrophage inflammatory protein (MIP) 1α and 1β.  In addition to being bound and activated by these chemokines, CCR5 is a coreceptor (together with CD4) for entry of the most common strain of HIV-1 into T cells. Thus maraviroc acts as an HIV entry inhibitor; this is the drug’s approved indication in the U.S. and in Europe. Maraviroc was discovered via a combination of high-throughput screening and optimization via standard medicinal chemistry.

New structural biology studies of the CCR5-maraviroc complex

Now comes a report in the 20 September 2013 issue of Science on the structure of the CCR5-maraviroc complex. This report was authored by a mainly Chinese group led by Beili Wu, Ph.D. (Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai); researchers at the University of California at San Diego and the Scripps Research Institute, San Diego were also included in this collaboration. A companion Perspective in the same issue of Science was authored by P. J. Klasse, M.D., Ph.D. (Weill Cornell Medical College, Cornell University, New York, NY).

As described in the Perspective, the outer surface of the HIV-1 virus displays numerous envelope protein (Env) trimers, each including the outer gp120 subunit anchored in the viral membrane by gp41. When gp120 binds to the cell-surface receptor CD4, this enables interaction with a specific chemokine receptor, either CCR5 or CXCR4. Interaction with both CD4 and the chemokine receptor triggers complex sets of changes in the Env complex, eventually resulting in the fusion of the viral membrane and the cell membrane, and the entry of the virus particle into the host cell.

HIV-1 gp120 makes contact with CCR5 at several points. The interactions between CCR5 and the variable region of gp120 called V3 are especially important for the tropism of an HIV-1 strain, i.e., whether the virus is specific for CCR5 (the “R5 phenotype”) or CXCR4 (the “X4 phenotype”). In the case of R5-tropic viruses, the tip of the V3 region interacts with the second extracellular loop (ECL2) of CCR5, while the base of V3 interacts with the amino-terminal segment of CCR5. Modeling of the interactions between the V3 domain of gp120 of either R5 or X4-tropic viruses with CCR5 or CXCR4 explains coreceptor use, in terms of forming strong bonds or–conversely–weak bonds and steric hindrance.

Monogram Biosciences (South San Francisco, CA) has developed and markets the Trofile assay. This is a molecular assay designed to identify the R5, X4, or mixed tropism of a patient’s HIV strain. If a patient’s strain is R5-tropic, then treatment with maraviroc is appropriate. However, a patient’s HIV-1 strain may undergo a tropism switch, or may mutate in other ways to become resistant to maraviroc.

Dr Wu and her colleagues determined the high-resolution crystal structure of the complex between maraviroc and a solubilized engineered form of CCR5. This included determining the CCR5 binding pocket for maraviroc, which was determined both by Wu et al’s X-ray crystallography, and by site-directed mutagenesis (i.e., to determine amino acid residues that are critical for maraviroc binding) that had been published earlier by other researchers.

The structural studies of Dr. Wu and her colleagues show that the maraviroc-binding site is different from the recognition sites for gp120 and for chemokines, as expected for an allosteric inhibitor. The X-ray structure shows that maraviroc binding prevents the helix movements that are necessary for binding of g120 to induce the complex sequence of changes that result in fusion between the viral and cellular membranes. (These helix movements are also necessary for induction of signal transduction by binding of chemokines to CCR5.)

Structural studies of CXCR4 and its inhibitor binding sites

In addition to their structural studies of the CCR5-maraviroc complex, Dr. Wu and her colleagues also published structural studies of CXCR4 complexed with small-molecule and cyclic peptide inhibitors in Science in 2010. These inhibitors are IT1t, a drug-like orally-available isothiourea developed by Novartis, and CVX15, a 16-residue cyclic peptide that had been previously characterized as an HIV-inhibiting agent. IT1t and CVX15 bind to overlapping sites in CXCR4. Other researchers have found evidence that the binding site for plerixafor also overlaps with the IT1t binding site.

As discussed in Wu et al’s 2013 paper, CCR5 and CXCR4 have similar, but non-identical structures. The binding site for IT1t in CXCR4 is closer to the extracellular surface than is the maraviroc binding site in CCR5, which is deep within the CCR5 molecule. The entrance to the CXCR4 ligand-binding pocket is partially covered by CXC4’s N terminus and ECL2, but the CCR5 ligand-binding pocket is more open.

Mechanisms of CXCR4 and CCR5 inhibition, and implications for discovery of improved HIV entry inhibitors

The chemokine that specifically interacts with the CXCR4 receptor is known as CXCL12 or stromal cell-derived factor 1 (SDF-1). Researchers have proposed a hypothesis for how CXCL12 interacts with CXCR4; this hypothesis appears to be applicable to the interaction between other chemokines and their receptors as well. This hypothesis is know as the “two-step model” or the “two-site model” of chemokine-receptor activation. Under the two-site model, the core domain of a chemokine binds to a site on its receptor (known as the “chemokine recognition site 1” or “site 1”) defined by the receptor’s N-terminus and its ECLs. In the second step, the flexible N-terminus of the chemokine interacts with a second site (known as “chemokine recognition site 2” or “site 2” or the “activation domain”) deeper within the receptor, in transmembrane domains. This result in activation of the chemokine receptor and intracellular signaling.

Under the two-site model, CXCR4 inhibitors (e.g., IT1t, CVX15, and  plerixafor), which bind to sites within the ECLs of CXCR4, are competitive inhibitors of binding of the core domain of CXCL12 to CXCR4 (i.e.., step 1 of chemokine/receptor interaction). They are thus orthosteric inhibitors of CXCR4. (This is contrary to the earlier assignment of plerixafor as an allosteric inhibitor of CXCR4.)  The CCR5 ligand maraviroc, however, binds within a site within the transmembrane domains of CCR5, which overlaps with the activation domain of CCR5. Dr. Wu and her colleagues propose two alternative hypotheses: 1. Maraviroc may inhibit CCR5 activation by chemokines by blocking the second step of chemokine/chemokine receptor interaction, i.e., receptor activation. 2. Maraviroc may stabilize CCR5 in an inactive conformation. It is also possible that maraviroc inhibition of CCR5 may work via both mechanisms.

Dr. Wu and her colleagues further hypothesize that the interaction of  HIV-1 gp120 with CCR5 (or CXCR4) may operate via similar mechanisms to the interaction of chemokines with their receptors. As we discussed earlier in this article, the base (or the stem region) of the gp120 V3 domain interacts with the amino-terminal segment of CCR5. The tip (or crown) of the V3 domain interacts with the ECL2 of CCR5, and–according to Dr. Wu and her colleagues–also with amino acid residues inside the ligand binding pocket; i.e., the activation site of CCR5. The HIV gp120 V3 domain may thus activate CCR5 via a similar mechanism to the two-step  model utilized by chemokines.

Based on their structural biology studies, Dr. Wu and her colleagues have been building models of the CCR5-R5-V3 and CXC4-X4-V3 complexes, and are also planning to determine additional structures needed to fully understand the mechanisms of HIV-1 tropism. The researchers will utilize their studies in the discovery of improved, second-generation HIV entry inhibitors for both R5-tropic and X4-tropic strains of HIV-1.

The bigger picture

The 17 October 2013 issue of Nature contains a Supplement entitled “Chemistry Masterclass”. In that Supplement is an Outlook review entitled “Structure-led design”, by Nature Publishing Group Senior Editor Monica Hoyos Flight, Ph.D. The subject of this article is structure-based drug design of modulators of GPCRs.
This review outlines progress in determining GPCR structures, and in using this information for discovery of orthosteric and allosteric modulators of GPCRs.

According to the article, the number of solved GPCR structures has been increasing since 2008, largely due to the efforts of the Scripps GPCR Network, which was established in that year. Dr. Wu started her research on CXCR4 and CCR5 as a postdoctoral researcher in the laboratory of Raymond C. Stevens, Ph.D. at Scripps in 2007, and continues to be a member of the network. The network is a collaboration that involves over a dozen academic and industrial labs. Its goal has been to characterize at least 15 GPCRs by 2015; it has already solved 13.

Interestingly, among the solved GPCR structures are those for the corticotropin-releasing hormone receptor and the glucagon receptor. Both have peptide ligands, and thus work by forming PPIs.

One company mentioned in the article, Heptares Therapeutics (Welwyn Garden City, UK), specializes in discovering new medicines that targeting previously undruggable or challenging GPCRs. In addition to discovering small-molecule drugs, Heptares, working with monoclonal antibody (MAb) leaders such as MorphoSys and MedImmune, is working to discover MAbs that act as modulators of GPCRs. Among Heptares’ targets are several GPCRs with peptide ligands.

Meanwhile, Kyowa Hakko Kirin Co., Ltd. has developed the MAb drug mogamulizumab (trade name Poteligeo), which is approved in Japan for treatment of relapsed or refractory adult T-cell leukemia/lymphoma. Mogamulizumab targets CC chemokine receptor 4 (CCR4).

Thus, aided in part by structural biology, the discovery of novel drugs that target GPCRs–including those with protein or peptide targets such as chemokine receptors–continues to make progress.


As the producers of this blog, and as consultants to the biotechnology and pharmaceutical industry, Haberman Associates would like to hear from you. If you are in a biotech or pharmaceutical company, and would like a 15-20-minute, no-obligation telephone discussion of issues raised by this or other blog articles, or of other issues that are important to  your company,  please contact us by phone or e-mail. We also welcome your comments on this or any other article on this blog.