Ralph M. Steinman, MD of the Rockefeller University (New York, NY) the discoverer of the dendritic cell and its central role in the immune system, died on September 30, 2011 at age 68 after a four-and-a-half year battle with pancreatic adenocarcinoma. On October 3, 2011, he was awarded half of the The Nobel Prize in Physiology or Medicine for 2011 “for his discovery of the dendritic cell and its role in adaptive immunity”. (The other half of the Prize was shared between Bruce A. Beutler and Jules A. Hoffmann “for their discoveries concerning the activation of innate immunity”.)

Previously, in 2007, Dr. Steinman had been awarded an Albert Lasker Basic Medical Research Award for the discovery of dendritic cells.

Dendritic cells are the principal antigen-presenting cells (APCs) in the immune system. They process antigenic material (for example, from invading bacteria and viruses, and from cancer cells), and present antigens on their surfaces to other types of immune cells, especially T cells. This results in antigen-specific activation of the T cells. Dendritic cells thus serve as the principal link between the innate and the adaptive immune system.

Nobel Prizes are not awarded posthumously, but the Nobel Committee was not aware that Dr. Steinman had died when they made the award. So the award still stands. Dr. Steinman thus has the distinction of being the only person to be awarded a Nobel Prize posthumously. The Nobel Foundation said, after reviewing the case, “The decision to award the Nobel Prize to Ralph Steinman was made in good faith, based on the assumption that the Nobel Laureate was alive.”

Nature published a “News in Focus” article on Dr. Steinman in its 13 October 2011 issue, written by Lauren Gravitz, a freelance writer and editor based in Los Angeles, California. The article details the attempt by Dr. Steinman and his colleagues to use dendritic cell-based immunotherapy to treat Dr. Steinman’s own cancer.

Ms. Gravitz met Dr. Steinman during her two-year tenure as a science writer in the Rockefeller University communications department.  While she was there, Dr. Steinman educated her on the complex field of dendritic cell biology. It was also during her time at Rockefeller that Dr. Steinman was diagnosed with advanced pancreatic cancer (in March 2007). Starting at the time of his diagnosis, Dr. Steinman and his colleagues began developing and using their experiential immunotherapies against that cancer. Thus Ms. Gravitz has been following this story from the beginning, and the October 2011 Nature article is the result.

An approved and marketed dendritic cell-based immunotherapy

Only one dendritic cell-based immunotherapy, Dendreon’s Sipuleucel-T (APC8015, Provenge) for treatment of advanced prostate cancer, has been approved by the FDA. The FDA approved it on April 29, 2010, and it is considered the first approved and marketed cancer vaccine. Sipuleucel-T was the first therapeutic cellular immunotherapy for cancer to demonstrate efficacy in Phase 3 clinical trials; this led to the FDA approval. However, Sipuleucel-T only extended mean survival by four months as compared to placebo in Phase 3 clinical trials. And the treatment is expensive, costing a total of $93,000 for the full treatment of three infusions.

Since Sipuleucel-T must be prepared specifically for each patient, using the patients own dendritic cells, a discussion of this product is relevant to the case of Dr. Steinman’s experimental treatment, which also involved autologous dendritic cells.

To prepare Sipuleucel-T, a patient’s autologous dendritic cells are purified from his or her blood. The cells are then sent to a Dendreon site, where they are incubated with a fusion protein, consisting of two moieties–the antigen prostatic acid phosphatase (PAP), which is present in 95% of prostate cancer cells, and a granulocyte-macrophage colony stimulating factor (GM-CSF) moiety, which is an immune cell activator. The resulting product, APC8015 or Sipuleucel-T, is returned to the infusion center and infused into the patient. The goal is to stimulate an immune response to tumor cells carrying the PAP antigen.

Although Sipuleucel-T is the the first therapeutic cellular immunotherapy for cancer to demonstrate efficacy in Phase 3 clinical trials in terms of overall survival, neither it, nor other cancer vaccines in clinical trials, gives complete responses. In our April 27, 2011 blog post, we discussed another therapeutic cellular immunotherapy for cancer, known as adoptive immunotherapy, which does give some complete responses in metastatic melanoma. However, this therapy is experimental and difficult to standardize, and has thus attracted no commercial interest. It is not approved by the FDA, and will not be covered by third-party payers. Thus the emphasis on dendritic cell vaccines.

Using dendritic cells to stimulate immune responses to Dr. Steinman’s pancreatic cancer

There are no approved cancer vaccines for pancreatic adenocarcinoma, which has a poor prognosis (survival measured in weeks or a few months in advanced cases). The disease is generally treated with the cytotoxic drug gemcitabine (Lilly’s Gemzar). However, this treatment appears to be mainly palliative in patients with advanced pancreatic cancer, giving an improved quality of life and a 5-week improvement in median survival. Most patients soon develop resistance to treatment with this agent. Thus, when Dr. Steinman (with the help of his colleagues) attempted to treat his own pancreatic cancer, he was venturing into the unknown.

According to Ms. Gravitz’ article, Dr. Steinman had a meeting with two immunotherapy researchers who had formerly been members of his lab–Michel Nussenzweig of Rockefeller and Ira Mellman of Genentech, shortly after he had been diagnosed with pancreatic cancer. The three planned a strategy to design potential therapies for Dr. Steinman’s cancer.  Dr. Nussenzweig would implant some of the tumor as xenografts in mice so that there would be enough material to work with. Dr. Mellman would start a cell line, so that drugs could be screened for activity in killing the cells. Other colleagues would look for mutations in tumor cell DNA that could be used to design drug treatments, and another would isolate surface peptides from the tumor cells so that they could be used as the basis of a vaccine. Meanwhile, Dr. Steinman would undergo conventional chemotherapy with gemcitabine  in combination with whatever experimental therapies that might be deemed to have potential to treat the cancer.

Dr. Steinman tried eight experimental therapies, one at a time. For each of these treatment, he and his colleagues submitted a single-patient, compassionate-use protocol to the FDA, and received approval from the agency. Among these treatments were three cancer vaccines. One of them was a form of BioSante’s GVAX (now Aduro’s GVAX, as of the February 2013 acquisition) . The product GVAX Pancreas for pancreatic cancer (which is now in clinical trials) is based on human pancreatic cell lines that have been engineered to secrete GM-CSF, and have then been lethally irradiated. In the case of Dr. Steinman’s treatment, cells from his own tumor were used instead of cell lines.

The other two cancer vaccines were dendritic cell-based immunotherapies, and used dendritic cells isolated from Dr. Steinman’s own blood. The first of these immunotherapies was developed by Argos Therapeutics (Durham, NC), of which Dr. Steinman was a cofounder. It involved transfecting Dr. Steinman’s dendritic cells with RNA derived from his own tumor. The resulting dendritic cells expressed tumor antigens on their surfaces, and were injected back into Dr. Steinman’s blood to potentiate the production of tumor antigen-specific T cells. The second immunotherapy, developed by researchers at the Baylor Institute for Immunology Research (Dallas, TX) involved loading Dr. Steinman’s dendritic cells with peptide antigens from the surface of his tumor. These were also injected back into Dr. Steinman’s blood, in order to potentiate a tumor-specific immune response.

Dr. Steinman also wanted to try combination therapies with ipilimumab. Dr. Steinman tried ipilimumab as a monotherapy, but never got the permissions needed to try the combination therapy. Ipilimumab is an immunomodulator that blocks cytotoxic T-lymphocyte-associated antigen 4 (CTLA4) (a cell surface protein that transmits an inhibitory signal to T cells) to potentate an antitumor T-cell response. The FDA refused permission for the combination therapy despite his belief, and that of other leading immunologists, that the cancer vaccines were likely to work better in combination with ipilimumab. Ipilimumab (Medarex/Bristol-Myers Squibb’s Yervoy) was approved by the FDA in March 2011, and clinical trials of combination therapies of ipilimumab and dendritic-cell vaccines are in early stages.

The course of Dr. Steinman’s disease

Patients with advanced pancreatic adenocarcinoma typically have a poor prognosis. The median survival for locally advanced and for metastatic pancreatic cancer (advanced pancreatic cancer represents over 80% of individuals diagnosed with the disease) is about 10 and 6 months respectively. For all stages of pancreatic cancer combined, the 1- and 5-year relative survival rates are 25% and 6%, respectively.

However, Dr. Steinman survived for four-and-a-half years!

Did any of the treatments that Dr. Steinman received extend his life? No one can know, since with a one-patient experimental treatment there are neither controls nor statistical data as in properly controlled clinical trials.

Dr. Steinman appeared to be much more responsive to gemcitabine than is usually the case. And he had a measurable antitumor immune response, since approximately 8% of his cytotoxic T cells targeted his cancer. Was this due to his natural immunity, or due to the dendritic cell immunotherapies and/or other treatments that he received? Did Dr. Steniman’s antitumor immune response make his cancer more susceptible to gemcitabine than is usually the case? There is no way to know.

The implications of Dr. Steinman’s one-patient experimental treatment

According to Lauren Gravitz’ article, despite these unanswerable questions, Dr. Steinman’s treatment helped move the cancer vaccine field forward. For example, it showed that the leaders in the cancer vaccine field can work together as a team to design and carry out therapies. It also showed that conventional chemotherapy can be given in combination with cancer vaccines. And it also bolstered Dr. Steinman’s passionate belief that it is vitally important to move beyond in vitro studies and animal models into human studies of dendritic cell vaccines, especially given the limitations of animal models.

With respect to animal models and dendritic cell vaccines:

• Dendritic cell immunotherapies designed for use in humans cannot be directly tested in standard animal models. For example, species specificity issues made direct testing of Sipuleucel-T in rodents impossible. Therefore, in preclinical studies researchers constructed “rodent equivalents” of Sipuleucel-T. These consisted of rodent APCs loaded with fusion proteins composed of either rat PAP (rPAP) fused to rat GM-CSF (rPAP•rGM-CSF) or human PAP (hPAP) fused to murine GM-CSF (hPAP•mGM-CSF), and these surrogate versions of Sipuleucel-T were tested in rodents.

• Autologous dendritic cell immunotherapies have proven to be “remarkably safe” in human studies. Therefore, it may not be necessary to test for safety in animal models.

• Dendritic cell biology is complicated. For example, researchers are still attempting to identify human dendritic cell subsets that correspond to known mouse dendritic cell subsets, especially subsets that appear to be the most promising for vaccine design. Therefore, the results of studies carried out in mice may not be directly applicable to humans. Moreover, the use of rhesus macaques for translational studies of vaccines based on dendritic cell biology is expensive.

Should autologous dendritic cell immunotherapies/vaccines for cancer be tested directly in humans, without the use of animal models for preclinical studies? In the case of the treatment of Dr. Steinman, the FDA allowed this to happen. Authorities in the field and regulatory agencies need to continue to discuss this issue.

Meanwhile, as stated at the end of Ms. Gravitz’ article, Anna Karolina Palucka of Baylor, a researcher who had been involved in Dr. Steinman’s treatment, says that she and her colleagues at Baylor are developing an immunotherapy program against pancreatic cancer based on the data from Dr. Steinman’s one-person trial. And Baylor will honor Dr. Steinman by opening a Ralph Steinman Center for Cancer Vaccines. This will be one of many tributes to a pathbreaking physician/scientist.
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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 click here. We also welcome your comments on this or any other article on this blog.

 

In recent months, there have been quite a few articles on the need to fix the clinical trial system. Among the most recent articles is the one by Boston-based Nature writer Heidi Ledford, Ph.D. published as a News Feature in the 29 September issue of Nature. In my humble opinion, this is the best article on the subject among those that have been published recently.

The pharmaceutical/biotechnology industry is frustrated with the increasing expense and the low output of the clinical trial system. This low productivity is economically unsustainable. The current clinical trial paradigm is over 50 years old. Back in the 1960s, the norm was to conduct single trials at single sites, each designed to answer a single question.

Nowadays, the norm is the large, multicenter clinical trial, especially for Phase 3 trials. “Multicenter” means that a trial is conducted at multiple sites, often in different countries, and could involve thousands of investigators and staff members. As pointed out in Dr.Ledford’s article, the large trials are mandated by the need in our more risk-adverse world to detect safety issues that occur in only a small percentage of patients, and to obtain good statistics for drugs that confer only a small benefit over the standard of care. However, certain major diseases require large trials of long duration even for drugs that may confer large benefits. For example, because the percentage of patients per year in cardiovascular disease (CVD) trials who experience cardiovascular events is small, these trials must be large and multiyear, in order to see any benefit even for a breakthrough drug.

The advent of personalized medicine–developing drugs and combinations of drugs that are specific for the molecular mechanism behind a patient’s disease–has put additional burdens on the clinical trial system. A disease may be found to be a collection of rare diseases in terms of mechanistic subtypes, each of which affects only a small number of people. This makes patient recruitment difficult.

As stated by Dr.Ledford, “Solving the problem may require fundamental changes to the clinical-trial system to make it faster, cheaper, more adaptable and more in tune with modern molecular medicine.”

Don’t use an “e-commerce” approach to determining drug efficacy!

Other commentators have recently noted the need to make clinical trials “faster, cheaper, and more adaptable.” Several of them have suggested bringing in strategies from other industries, especially e-commerce and social media.

For example, in an editorial published in the 23 September issue of Science, Andrew Grove, the former Chief Executive Officer of Intel, proposes moving towards an “e-trial” system, based on such large-scale e-commerce platforms as that of Amazon.com. Under the proposed e-trial system, the FDA would ensure safety only, not efficacy, and would continue to regulate Phase 1 trials. Once Phase 1 trials have been successfully completed, patients would be able to obtain a new drug through qualified physicians.

Patients’ responses to a drug would be stored in a database, along with their medical histories. There would be measures to protect a patient’s identity, and the database would be accessible to qualified medical researchers as a “commons.” The response of any patient or group of patients to a drug or treatment could then be tracked and compared to those of others in the database who were treated in a different manner or were untreated. These comparisons would provide insights into a drug’s efficacy, and how individuals or subgroups (perhaps defined in part via biomarkers) respond to the drug. This would liberate clinical trials from the “tyranny of the average” that characterize most trials today. As the database grows over time, analysis of the data would also provide information needed for postmarketing studies and comparative effectiveness studies.

Dr. Grove’s proposal is one of several in which the mandate of the FDA (and regulatory agencies in Europe, Japan, etc.) is to regulate safety only (via Phase 1 clinical trials) not efficacy. Efficacy is then determined via some sort of open system, with information gathered and provided to patients and physicians electronically, via systems reminiscent of e-commerce or social media.

We are opposed to removing efficacy from the oversight of the FDA and other regulatory agencies. There are two reasons for this, both of which are illustrated graphically in Box 1 of Dr. Ledford’s article, entitled “the clinical trial cliff”. Approximately half of Phase 2 clinical trials between 2008 and 2010 failed due to inability to demonstrate efficacy. (Around one-third of Phase 2 failures were due to safety, and the remaining failures were mainly due to strategic decisions to terminate a drug.) Among Phase 3 failures between 2007 and 2010, around two-thirds were due to efficacy, and around one-quarter were due to safety. These results indicate that the majority of drugs entered into clinical trials lack efficacy.

The second reason is that many safety problems–especially the rarer safety issues that occur in only a small percentage of patients–are typically not detected in Phase 1, but in Phase 3 and even the postmarking period.

Reduce clinical attrition with new trial designs and improved animal models

Dr. Ledford’s proposals for fixing clinical trials leave regulatory agencies in charge of overseeing both safety and efficacy. They mainly focus on improving clinical trials by reducing “attrition”–i.e., failure of drugs in the clinic, especially in Phase 2 and Phase 3, and on improving patient recruitment. Haberman Associates has produced publications–as well as articles on this blog–during the 2009-2011 period that provide a more in-depth discussion of strategies for reducing attrition than is possible in a 3-page article such as Dr. Ledford’s.

Two of Dr. Ledford’s strategies involve modifications of clinical trial design. Both of these are discussed in Chapter 6 of our book-length Cambridge Healthtech Institute (CHI) Insight Pharma Report, Approaches to Reducing Phase II Attrition. The first is the “Phase 0” trial. This is a type of pre-Phase 1 clinical trial, which uses microdoses of a drug to assess such parameters as pharmacokinetics and target occupancy. As Dr. Ledford suggests, in some cases Phase 0 trials can reduce or eliminate pharmacological testing in animals, and allow researchers to get human data more quickly.

The other trial design strategy mentioned in Dr, Ledford’s article is the use of adaptive clinical trials. This type of trial allows researchers to change the course of a trial in response to trial results. For example, this may mean assigning new patients to specific doses, changing the numbers of patients assigned to each arm of a trial, and changes in hypotheses or endpoints. Monitoring and changing the trial is typically done by an independent data monitoring committee [DMC] so that ideally, double-blind conditions are maintained.

As Dr. Ledford states, adaptive clinical trials may result in shortening the time and cost of the clinical trial process. But, as with Phase 0 microdosing trials, there are many controversies surrounding adaptive clinical trials. Both of these strategies are works in progress.

The other strategy for reducing attrition discussed in Dr. Ledford’s article is to use improved animal models (i.e., animal models designed to more faithfully model human disease) in preclinical studies. We discussed this strategy in Approaches to Reducing Phase II Attrition, and in greater detail in another book-length report, Animal Models for Therapeutic Strategies. I also recently led the workshop “Developing Improved Animal Models in Oncology and CNS Diseases to Increase Drug Discovery and Development Capabilities” at Hanson Wade’s 2011 World Drug Targets Summit.

Several articles on our Biopharmconsortium Blog also focus on improved animal models for predicting efficacy of drug candidates in discovery research and in preclinical studies. Our April 15, 2010 blog post, based on an article in The Scientist, focused on “co-clinical mouse/human trials”. This type of clinical trial was developed by Pier Paolo Pandolfi, MD, PhD (Director, Cancer and Genetics Program, Beth Israel-Deaconess Medical Center Cancer Center and the Dana-Farber/Harvard Cancer Center) and his colleagues.

These trials utilize genetically engineered transgenic mouse strains that have genetic changes that mimic those found in specific human cancers. These mouse models spontaneous develop cancers that resemble the corresponding human cancers. In the co-clinical mouse/human trials, researchers simultaneous treat a genetically engineered mouse model and patients with tumors that exhibit the same set of genetic changes with the same experimental targeted drugs. The goal is to determine to what extent the mouse models are predictive of patient response to therapeutic agents, and of tumor progression and survival. The studies may thus result in validated mouse models that are more predictive of drug efficacy than the currently standard xenograft models.

The new Ledford Nature article discusses co-clinical trials as a means to develop more predictive animal model studies–not only using improved, potentially more predictive animal models, but also treating these animals in similar way (in terms of doses, formulations, schedules of medication, etc.) to the humans in the parallel human clinical trial.

The Ledford article mentions the animal-model portion of a co-clinical trial, which was published in January 2011. This trial utilized two genetically-engineered PDGF (platelet-derived growth factor)-driven mouse models of the brain tumor glioblastoma multiforme (GBM), one of which has an intact PTEN gene and the other of which is PTEN deficient.

Unlike the “standard” mouse xenograft models, these models more closely mimicked the human disease, including growth of tumors within the brain, not subcutaneously. Thus any drug administered to these mice systemically (e.g., intraperitoneally, as was done in this study) had to cross the blood-brain barrier (BBB), as in the case of human clinical trials. This would not be the case with a standard xenograft model, which is one deficiency of these models for brain tumors such as GBM.

GBM is both the most common and the most malignant primary brain tumor in adults. It has a poor prognosis. PDGF-driven GBMs, which results from deregulation of the PDGF receptor (PDGFR) or overexpression of PDGF, account for about 25-30% of human GBMs. These mutations result in the activation of the phosphatidylinositol 3-kinase (PI3K)/Akt/mammalian target of rapamycin (mTOR) pathway. These tumors may also exhibit mutation or loss of heterozygosity of the tumor suppressor PTEN, which also upregulates the PI3K/Akt/mTOR pathway.

The researchers tested the Akt inhibitor perifosine (Keryx Biopharmaceuticals, an alkylphospholipid) and the mTOR inhibitor CCI-779 (temsirolimus; Pfizer’s Torisel; originally developed by Wyeth prior to the Pfizer merger and approved for treatment of renal cell carcinoma), both alone and in combination, in vitro and in vivo. Specifically, the drugs and drug combinations were tested in cultured primary glioma cell cultures derived from the PTEN-null and PTEN-intact mouse PDGF-driven GBM models, and in the animal models themselves.

The studies showed that both in vitro and in vivo, the most effective inhibition of Akt and mTOR activity in both PTEN-intact and PTEN-null cells or animals was achieved by using both inhibitors in combination.  In vivo, the decreased Akt and mTOR signaling seen in mice treated with the combination therapy correlated with decreased tumor cell proliferation and increased cell death; these changes were independent of PTEN status. The co-clinical animal study also suggested new ways of screening GBM patients for inclusion in clinical trials of treatment with perifosine and/or CCI-779.

According to Dr. Ledford’s Nature article, the National Cancer Institute (NCI) invested $4.2 million in Dr. Pandolfi’s co-clinical trials in prostate and lung cancer in 2009. In addition to the co-clinical trials with genetically-engineered mouse models run by Dr. Pandolfi and others, researchers at the Jackson Laboratory are conducting co-clinical trials with mouse xenograft models that receive tumor cells from patients to be treated in human clinical trials.

Use patient registries in recruitment of patients for clinical trials

In Dr, Ledford’s article, she discusses a crucial factor other than clinical attrition that hinders progress in conducting clinical trials–patient recruitment. According to the article, at least 90% of trials are extended by at least six weeks because of failure to enroll patients on schedule. Only about one-third of the sites involved in a typical multicenter trial manage to enroll the expected number of patients. As a result, clinical trials are longer and more expensive, and some of them are never completed.

Personalized medicine, in which researchers use biomarkers or other criteria to determine what fraction of patients with a particular disease are eligible for a trial (e.g., cancer patients with an activating mutation in a kinase that is the target of the drug to be tested), makes recruitment harder. That is because researchers must screen large numbers of patients to identify the fraction of patients that would be eligible for the trial. So they need to recruit (and screen) a much larger number of patients than in conventional clinical trials with no patient stratification.

Therefore, researchers, “disease organizations”, and patient advocates are devising new strategies to facilitate recruitment of eligible volunteers. Dr. Ledford cites the example of the Alpha-1 Foundation (Miami, Florida), a “disease organization” that focuses on the familial disease alpha-1 antitrypsin deficiency. (This disease renders patients susceptible to lung and liver diseases.) This foundation has  created a registry of patients with alpha-1 antitrypsin deficiency who are willing to be contacted about and to participate in clinical trials.

There are also cancer registries. Dr. Ledford mentions the Total Cancer Care program run by the Moffitt Cancer Center (Tampa, Florida). This program, which involves 18 hospitals, compiles medical history, tissue samples (stored for future analysis) and genetic information about each patient’s tumor. Patients can consent to doctors contacting them about trials. There are other similar programs being developed in the Netherlands and elsewhere. Dr.Ledford mentions the difficulty in negotiating agreements between institutions, and the need for adequate, ultra-secure networks to support registries that connect multiple hospitals and research centers.

Patient registries that are designed to proactively support recruitment for clinical trials have some resemblance to a “social media” approach to recruitment. However, there is a big difference–the need to secure the privacy of patient records. The current trend in social media (and in some e-commerce platforms) is anti-privacy. This is yet another important reason why a social media or e-commerce approach to clinical trials or other aspects of biotech/pharma R&D is not a suitable model. (To his credit, Dr. Grove mentions the need to maintain patient privacy and confidentiality. But this is not the norm with e-commerce and social media.)

Cutting red tape for faster and cheaper clinical trials

Dr Ledford also mentions ways to deal with more bureaucratic issues that can slow down or block the progress of clinical trials. The NCI is now initiating a data-management system that will standardize data entry across all 2,000 sites that conduct NCI-sponsored trials. This should help reduce costs and cut down on record-keeping errors and omissions.The FDA is also looking into ways to reduce reporting requirements and paperwork. so that investigators can submit summaries of case reports rather than each individual document.

To adapt to the multicenter nature of clinical trials, the US Office for Human Research Protections (Rockville, Maryland), which oversees NIH-funded human studies, has proposed changes to its guidelines that would require designation of a single review board for each project. This may greatly improve the current situation, in which multicenter trials must get approval from each center’s institutional review board. This can take months or even years. Despite the definite advantages of more centralized review, individual research centers may be reluctant to give up their direct oversight of clinical trials.

Something important was not in Dr. Ledford’s article

The space limitations for Dr. Ledford’s “News Feature” article, plus its strict focus on clinical trials per se, did not permit her to include something of crucial importance to reduce clinical attrition. That is utilizing such strategies as biology-driven drug discovery in the research phase of drug development. These strategies are designed to select the best targets and to discover drugs that are more likely to be efficacious in treating a particular group of patients. These research strategies are then coupled with early development strategies that emphasize designing clinical trials aimed at obtaining rapid proof of concept in humans. Such trials typically involve the use (and often the discovery) of biomarkers.

We discussed these issues extensively in our report, Approaches to Reducing Phase II Attrition, as well as in an article published in Genetic Engineering and Biotechnology News (and available on our website) “Overcoming Phase II Attrition Problem“. We also discussed a specific case of the use of this strategy in our October 25, 2010 article on this blog.

Conclusions

Given the low productivity of pharmaceutical R&D, it is tempting to take an envious look at the success of e-commerce and social media, and to attempt to devise strategies that apply methodologies from these industry sectors to the biotech/pharmaceutical industry. We should remember, however, that not so long ago some pharmaceutical executives attempted to apply methodologies from such industries as aerospace, computer hardware, and the auto industry to pharma R&D. Not only did that not work too well for the pharmaceutical industry, but as we all know, the industries that served as a model for these approaches haven’t done very well in recent years either.

In contrast, pharmaceutical and biotechnology companies that have formulated strategies that embrace the uniqueness of biology, such as Novartis and Genentech (the latter now merged with Roche), have done a lot better.

There are other strategies for making clinical trials faster, cheaper, and better that are now under discussion in the biotech/pharma industry and the FDA.  These strategies are based on clinical experience, not e-commerce. We shall discuss them in further blog posts.

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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 click here. We also welcome your comments on this or any other article on this blog.

 

This article is an update of a three-part series on insulin sensitizers for treatment of type 2 diabetes that was published on this blog in August and September of 2010.

Summary of our August/September 2010 blog articles on insulin sensitizers

In part 1 of the series (posted August 23, 2010), we focused on safety issues with the two marketed thiazolidinedione (TZD) peroxisome proliferator-activated receptor gamma (PPARγ) agonists–rosiglitazone (GlaxoSmithKline’s Avandia) and pioglitazone (Takeda’s Actos). Both of these insulin sensitizing, antidiabetic agents induce weight gain, and carry an increased risk of edema and heart failure. In addition, rosiglitazone carries an increased risk of myocardial infarction. On September 23, 2010, the FDA restricted access to Avandia, and the European Medicines Agency (EMA) recommended that the drug be pulled from the market.

In part 2 of the series (posted on August 29, 2010), we discussed a breakthrough discovery by Bruce Spiegelman (Dana-Farber Cancer Institute and Harvard Medical School, Boston MA) and his colleagues, published in the 22 July 2010 issue of Nature. It was the Spiegelman group that originally identified PPARγ as the master regulator of adipocyte biology and differentiation, which eventual led to the development of the TZD drugs.

In that research, the Spiegelman group found evidence that the insulin sensitizing and antidiabetic effects of PPARγ agonists may not be due to the agonistic effects of these compounds on PPARγ, but to their ability to inhibit phosphorylation (at Ser 273) of PPARγ by the enzyme cyclin-dependent kinase 5 (CDK5). A weak PPARγ agonist, the benzoyl 2-methyl indole (non-TZD) MRL24, inhibits CDK5 phosphorylation of PPARγ as well as rosiglitazone, and also has very good antidiabetic activity.

CDK5 phosphorylation of PPARγ does not change the ability of PPARγ to upregulate transcription of genes involved in adipocyte differentiation. However, it inhibits the ability of PPARγ to upregulate transcription of a set of genes, including the gene for the adipokine adiponectin, that induce insulin sensitivity and resistance to obesity. Although both rosiglitazone and MRL24 inhibit CDK5 phosphorylation of PPARγ, treatment with the strong agonist rosiglitazone results in upregulation of both the adipogenic and the pro-insulin resistance sets of genes, while treatment with MRL24 results only in upregulation of the pro-insulin resistance set.

Researchers hypothesize that it is the upregulation of the adipogenic gene set that is responsible for the adverse effects of strong agonists of PPARγ–weight gain, edema, and the risk of heart failure. In contrast, the upregulation of adiponectin and the other members of the pro-insulin resistance gene set is thought to be responsible for the desirable, antidiabetic effect of PPARγ agonists.

In part 3 of the series (published on September 16, 2010), we discussed two essays, also published in the 22 July 2010 issue of Nature, that discuss using the new breakthrough results of the Spiegelman group to discover and develop improved insulin sensitizers. These essays recommended that researchers screen for compounds that inhibit CDK5 phosporylation of PPARγ rather than those that are strong PPARγ agonists. We also discussed the prospects for early-stage non-TZD partial or selective agonists of PPARγ, which might constitute second-generation insulin sensitizers.

New research from the Spiegelman group based on their 2010 breakthrough result

On September 4, 2011, Nature published, as an “advance online publication”, a new paper [subsequently published in Nature’s 22 September 2011 print edition] by Bruce Spiegelman, Patrick R. Griffin and Theodore Kamenecka (Scripps Research Institute, Jupiter, Florida) and their colleagues on discovery of novel compounds that bind to PPARγ and block its phosphorylation by CDK5, and which completely lack PPARγ agonist activity. (These compounds are thus neither full nor partial/selective agonists of PPARγ.)

One of these compounds, SR1664, exhibited potent antidiabetic and insulin sensitizing activity in two mouse models of obesity-associated type 2 diabetes. However, unlike full agonists such as rosiglitazone, it did not cause fluid retention and weight gain in these animal models. Fluid retention and weight gain are major adverse effects of TZDs in their own right, and are also thought to be related to the even more serious cardiovascular adverse effects of TZDs. Moreover, SR1664 did not interfere with bone mineralization in cultured osteoblasts; this assay is a model for the loss of bone mineral density and increase risk of fracture seen with TZDs.

The researchers developed SR1664 by starting with a partial agonist of PPARγ developed by GlaxoSmithKline, known as compound 7b. Using compound 7b as a scaffold for chemical modification, the researchers optimized for (1) high binding affinity for PPARγ, (2) blocking of CDK5-mediated PPARγ phosphorylation and (3) lacking classical agonism. The structure of two resulting compounds, SR1664 and SR1824, are given in the new Spiegelman/Griffin paper.

Although the new study suggests that SR1664 may be as efficacious an insulin sensitizer as TZDs without inducing their major adverse effects, the safety of these compounds in humans (as opposed to the mouse models) remains unproven. Moreover, SR1664 has unfavorable pharmacokinetic properties and is thus not a good candidate for development as a drug. According to a press release, Dr. Griffin’s molecular therapeutics group and Dr. Kamenecka’s medicinal chemistry group at Scripps have been using S1664 as a molecular scaffold for the discovery of derivatives with improved pharmacokinetic properties. They are advancing such newer compounds into additional studies.

Why develop new insulin sensitizers rather than depending on current antidiabetic drugs?

In Heidi Ledford’s commentary published in the 22 July 2010 issue of Nature, the author points out that some observers believe that pharmaceutical companies will be reluctant to attempt to develop new insulin sensitizers that target PPARγ, given the checkered history of that class of drugs. And other medical authorities believe that the older, inexpensive, and well proven type 2 diabetes drugs–insulin, metformin, and sulfonylureas–are adequate for the treatment of type 2 diabetes.

However, there remain important unmet needs in the treatment of type 2 diabetes. These especially include dealing with the relentlessly progressive nature of type 2 diabetes–for example, even patients who initially succeed in reaching glycemic goals with only diet/exercise and metformin will eventually need multidrug treatment, including insulin. Progression of type 2 diabetes is mainly due to the loss of pancreatic beta-cell function, which results in increased impairment of a patient’s ability to produce insulin in response to increased blood glucose.

Despite the major safety issues with TZDs, there is both animal model and human evidence that these agents may work to preserve and/or enhance beta-cell function. It will be important to determine if nonagonist second-generation insulin sensitizer candidates, such as those being developed by the Spiegelman and Griffin groups, also have the beta-cell preserving or enhancing effects of TZDs.

The Harvard/Scripps efforts to discover safer insulin sensitizers illustrate the potential role of academia (based on breakthrough science) in areas of drug discovery and development that industry is reluctant to undertake. However, although these academic groups might potentially take the nonagonist insulin sensitizers through lead optimization and preclinical studies, eventually industry (whether a biotech company or a pharmaceutical company) will need to take the compounds through clinical trials in order for any drugs to reach the market.
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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 click here. We also welcome your comments on this or any other article on this blog.

 

On Aug. 26, 2011, the FDA approved the kinase inhibitor crizotinib (Pfizer’s Xalkori, originally known as  PF-02341066) for treatment of patients with locally advanced or metastatic non-small cell lung cancer (NSCLC), in which tumor cells exhibit rearrangements in the anaplastic lymphoma kinase (ALK) gene. These rearrangements of the ALK gene constitute driver mutations that are critical for the malignant phenotype of lung adenocarcinomas that have the mutations.

Most ALK rearrangements in lung adenocarcinoma result from a deletion and inversion in chromosome 2, which produces EML4-ALK fusion genes. (EML4 refers to the echinoderm microtubule-associated protein-like 4 gene.) EML4-ALK rearrangements are found in about 4% to 5% of patients with NSCLC. This small percentage of lung cancer patients constitutes about 8,000 to 10,000 patients each year in the United States, and a worldwide patient population of around 40,000.

Crizotinib was approved together with a companion diagnostic, Abbott’s Vysis ALK Break Apart FISH Probe Kit, which is designed to help determine if a patient’s tumors have the abnormal ALK gene. The kit is designed to Identify all ALK gene rearrangements with fusion partners, including but not restricted to: EML4, TFG (TRK-fused gene), and KIF5B (kinesin family member 5B).

Crizotinib is the second targeted kinase inhibitor to be approved together with a companion diagnostic in recent weeks.  The first was vemurafenib (Plexxikon/Roche’s Zelboraf,  PLX4032), which we discussed extensively in this blog, and whose approval we covered in our August 19, 2011 article. Vemurafenib was approved together with Roche’s cobas 4800 BRAF V600 Mutation Test.

The discovery of crizotinib began with research at Sugen (San Francisco, CA), which had been acquired by Pharmacia which was subsequently acquired by Pfizer. The drug resulted from research aimed at discovery of a kinase inhibitor that targeted c-Met. The resulting drug, PF-02341066 (later known as crizotinib), is indeed a c-Met inhibitor, and was entered into Phase 1 clinical trials.  c-Met, or hepatocyte growth factor receptor, is a receptor kinase that has been implicated in cancer cell growth, migration, invasion, and metastasis.

Subsequent studies by Japanese researchers identified the inversion that results in the EML4-ALK fusion gene in a subset of human NSCLCs. They also showed that cultured mouse fibroblasts expressing the EML4-ALK fusion gene generated subcutaneous tumors in nude mice. The researchers hypothesized that the EML4-ALK fusion kinase would be a good therapeutic target, as well as a diagnostic biomarker for a companion diagnostic. Meanwhile,  researchers at Pfizer and the Massachusetts General Hospital found that PF-02341066/crizotinib was a multitargeted kinase inhibitor, which targets ALK in addition to c-Met. Pfizer researchers therefore began preclinical and clinical studies aimed at the commercialization of PF-02341066/crizotinib for treatment of patients with NSCLC carrying activating rearrangements of ALK.

Clinical trials of crizotinib in NSCLC patients with activating rearrangements of ALK

The safety and efficacy of crizotinib in NSCLC patients with activating rearrangements of ALK were established in two multi-center, single-arm studies, including a Phase 2 study (PROFILE 1005) and a Part 2 expansion cohort of a Phase 1 study (Study 1001). The studies enrolled a total of 255 patients with late-stage ALK-positive NSCLC. A sample of each patient’s tumor tissue was tested for ALK gene rearrangements before the patient could be enrolled in the study. The studies were designed to measure objective response rate, i.e., the percentage of patients who experienced complete or partial cancer shrinkage. Most patients in the studies had received prior chemotherapy.

In one study, the objective response rate was 50 percent with a median response duration of 42 weeks. In another, the objective response rate was 61 percent with a median response duration of 48 weeks.

The FDA based its approval of the Vysis ALK Break Apart FISH Probe Kit on data from one of the studies.

As part of the post-marketing requirements, Pfizer continues to evaluate critozinib in two confirmatory, randomized, open-label Phase 3 trials. In these trials, crizotinib is being compared with standard-of-care chemotherapy. One study is being carried out in previously treated patients with advanced ALK-positive NSCLC; the other trial is being carried out in previously untreated patients with advanced ALK-positive non-squamous NSCLC.

Crizotinib as a multitargeted ALK/c-Met kinase inhibitor

The epidermal growth factor receptor (EGFR) kinase inhibitors erlotinib (Genentech/Roche’s Tarceva) and gefitinib (AstraZeneca/Teva’s Iressa) are used for the treatment of patients with NSCLC with activating mutations in the intracellular kinase domain of EGFR. As with  crizotinib and vemurafenib, companion diagnostics are used to determine if a patient is likely to benefit from treatment with erlotinib or gefitinib. Activating mutations in EGFR are found in approximately 10–15% of Caucasian and 30–40% of Asian NSCLC patients.

As with most targeted antitumor drugs, acquired resistance to erlotinib or gefitinib develops in patients treated with these agents. The two most common mechanisms of this acquired resistance are:

• development of a secondary mutation that blocks binding of the inhibitors to EGFR kinase (responsible for about 50% of acquired drug resistance)
• amplification and/or activation of the c-Met kinase, or alternatively high-level expression of the natural ligand of c-Met, hepatocyte growth factor (HGF) (responsible for about 20% of acquired drug resistance).

As we discussed in Chapter 5 of our June 2011 book-length report Multitargeted Therapies: Promiscuous Drugs and Combination Therapies, Pfizer researchers and their academic collaborators found in 2010 that one could overcome HGF/c-Met-mediated resistance to erlotinib or gefitinib by combination therapy with an irreversible EGFR kinase inhibitor (such as PF-00299804) and a c-Met inhibitor (such as crizotinib/PF-02341066). The same researchers also developed a rationale for development of a companion diagnostic to identify patients with rare preexisting populations of cells with amplified c-Met genes. Such patients might be treated with the irreversible EGFR kinase inhibitor/c-Met kinase inhibitor combination. This would be expected to bypass the resistance that would develop after standard treatment with erlotinib or gefitinib alone.

Intriguingly, the 2010 Pfizer study thus suggests a second indication for crizotinib–use in combination therapy with an irreversible EGFR kinase inhibitor such as Pfizer’s PF-00299804 to overcome or preemptively circumvent HGF/c-Met-mediated resistance to the approved EGFR kinase inhibitors. However, Pfizer’s PF-00299804 is still in clinical trials, and has not yet been approved by any regulatory agency. Boehringer Ingelheim is also developing an irreversible EGFR kinase inhibitor, and Pfizer has another such agent, neratinib, in clinical trials.

Meanwhile, in addition to crizotinib, there are also other c-Met inhibitors in clinical development, including Daiichi Sankyo/ArQule’s ARQ197 and GSK/Exelixis’ XL880/GSK1363089 (now known as foretinib). ARQ197, which is in Phase 3 trials in NSCLC, is apparently the most advanced compound in development as a c-Met inhibitor.

An important potential use of irreversible EGFR kinase inhibitors is to overcome acquired resistance to first-generation EGFR kinase inhibitors in NSCLC patients due to development of a secondary blocking mutation in EGFR. The development of combination therapies of irreversible EGFR kinase inhibitors with c-Met inhibitors such as crizotinib and ARQ197 would enable their use in overcoming the second major mechanism of acquired resistance to EGFR inhibitors, via HGF/c-Met.

Conclusions

The approval of crizotinib, together with a companion diagnostic, for the treatment of ALK-driven NSCLC represents the newest example of a paradigm shift toward personalized medicine using targeted therapies in the treatment of cancer. Other examples include vemurafenib for the treatment of melanoma, and the original small-molecule targeted kinase inhibitor, imatinib (Novartis’ Gleevec/Glivec) for the treatment of chronic myelogenous leukemia (CML) and gastrointestinal stromal tumors (GISTs).

In lung cancer, the use of erlotinib and gefitinib to treat EGFR-driven NSCLC, which represents about 10-15% of cases in the U.S. and Western Europe, is yet another example, even though companion diagnostics for these agents had not yet been developed at the time of their introduction to the market. ALK-driven NSCLC represents yet another 4-5% of cases.

According to researchers at the Lung Cancer Mutation Consortium, nearly 60% of patients with lung adenocarcinoma have 1 of 10 genomic abnormalities for which there is an approved or experimental drug. Paul Bunn, M.D., of the University of Colorado School of Medicine (Aurora, CO) asks, “We have 2 drugs approved now for 2 molecular abnormalities. The question is, will we go 10 for 10?”.  Diagnostic technology for testing for these mutations is also moving forward, and according to Dr. Bunn, it is cheaper to test for all ten abnormalities than it used to be to test for one abnormality.

As we discuss in our June 2011 report, and in several articles on this blog, patients treated with targeted agents usually develop acquired resistance to these drugs. Researchers, with some initial success, have been working on developing drugs to overcome this resistance. This is thus an important aspect of the development of personalized medicine for cancer.

Both EGFR-driven and ALK-driven NSCLCs are usually found in non-smokers or light smokers, while most lung cancer is associated with smoking. Physicians who treat lung cancer, as well as patients, await the development of agents that can effectively treat lung cancer in smokers and former smokers. Smoking rates have been going down in many industrialized countries, including the U.S., but that is not uniformly true in all the world. Moreover, there are still large numbers of smokers and former smokers who are at risk for smoking-induced lung cancer, and lung cancer in never-smokers (which accounts for about 10-15% of lung cancer cases) is by no means a solved problem.

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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 click here. We also welcome your comments on this or any other article on this blog.

 

On July 29, 2011, Merck announced that It was shutting down the San Francisco research laboratory that it had acquired as part of its $1.1 billion acquisition of therapeutic RNAi specialist company Sirna Therapeutics. This announcement was covered in a July 29, 2011 article in Xconomy, and in a news brief in the 4 August issue of Nature and a linked Nature news blog article.

According to the Xconomy article, the shutdown will include the loss of around 50 jobs. Around ten people are being offered transfers to other Merck facilities in nearby Palo Alto CA and on the East Coast.

The Merck facility shutdown continues the exit or retrenchment from therapeutic RNAi research at other Big Pharma companies. The Biopharmconsortium Blog has covered these moves at Roche and Pfizer.

As we discussed in the Roche article, Novartis had also decided to end its 5-year partnership with therapeutic RNAi specialty company Alnylam In September 2010. However, Novartis acquired technology and exclusive development rights for RNAi therapeutics against 31 targets for in-house use as the result of its partnership with Alnylam.  Alnylam is entitled to receive milestone payments for any RNAi therapeutic products that Novartis develops based on these targets. Thus Novartis is still involved in RNAi therapeutics, despite the termination of the Alnylam partnership.

Moreover, according to the Nature news blog, Ian McConnell of Merck’s Scientific Affairs, R&D and Licensing and Partnerships said that Merck will continue to have over 100 scientists working on RNA-based therapeutics, and that it continues to invest significantly in the field. Closing the San Francisco lab represents an effort to trim the budget by eliminating the cost of maintaining a separate RNAi facility.

In our previous blog articles on Big Pharma RNAi therapeutics retrenchment, and in our October 2010 book -length report, RNAi Therapeutics: Second-Generation Candidates Build Momentum, we discussed the strategic issues that are involved in undertaking (or in retrenching from) R&D programs in RNAi therapeutics, and in investing in that area. The therapeutic RNAi (and microRNA) field represents an early-stage area of science and technology. The field may be technologically premature, as was the monoclonal antibody (MAb) drug field in the 1980s.

Big Pharma originally got into RNAi therapeutics in order to help fill weak pipelines, and with the hope of staking out a commanding position in the RNAi field once it became successful. However, with the short-term pressure at Big Pharma companies to cut expenses and programs, Big Pharmas have been losing the needed patience to continue with a technologically premature field like RNAi therapeutics.

In the June 2011 issue of Molecular Therapy, there is an editorial by Arthur Krieg, M.D. (former Chief Scientific Officer of the now-closed Pfizer Oligonucleotide Therapeutics Unit, and now Entrepreneur in Residence at Atlas Venture, Cambridge, MA), entitled “Is RNAi dead?” As discussed in the editorial, the move of Big Pharma away from RNAi, according to some observers, signals the death of the therapeutic RNAi platform. Dr. Krieg outlines an alternative view.

According to Dr. Krieg, Big Pharmas got into RNAi therapeutics with the hope of enabling the rapid development of targeted drugs without the long time lags and uncertainties of small molecule drugs and biologics. In theory, if a research team has a good target, it could rationally design a lead RNAi drug specific for the target and ready for human clinical trials within 15 months. And researchers would not have to worry about “undruggability” of targets. However, there have been several unforeseen hurdles to the development of RNAi drugs, the most formidable of which is the issue of drug delivery. Although certain high-profile publications suggested that the challenge of RNAi drug delivery could be easily overcome, this proved not to be the case in practice.

However, Dr. Krieg believes that the progress in RNAi delivery in recent years has been “nothing short of spectacular”. In 2008, the best RNAi delivery systems for a liver target might have an IC50 (i.e., the RNAi dose required for 50% inhibition of target expression) of 1–3 mg/kg, but in 2010/2011, the IC50 has been reduced to about 1% of this value, which is an improvement of two logs. Dr. Krieg also says that there have also been significant advances in reducing off-target and other undesired systemic effects of RNAi therapeutics in animal models in recent years.

Nevertheless, the advances in RNAi delivery and safety are moving too slowly for Big Pharma’s current short-term mindset. According to Dr. Krieg, if companies are not able to take an RNAi drug into clinical development this year, then the next time there is an R&D portfolio review, investments in “high-risk” technology platforms such as RNAi are likely to be cut. As we have discussed in this blog, and as is well-known to most of you, every Big Pharma company has been cutting R&D and shedding poorly productive and high-risk programs. The focus at many Big Pharmas is on fast, sure returns. High-risk or premature technologies that have not yet yielded any marketed drugs, such as RNAi (and for example, stem cells/regenerative medicine) is not likely to offer such returns.

Dr. Krieg also notes that in the case of another once-premature technology, monoclonal antibody (MAb) drugs, it took several waves of technology development to advance from repeated clinical failure to one of the most successful classes of drugs today. In our view, MAb technology is the classic case (in the life sciences, anyway) of how researchers and companies can take such a premature technology up the technology curve by developing enabling technologies. We discussed this case in our September 28, 2009 blog article, and its applicability to RNAi and stem cells in our July 13, 2009 blog article. As discussed in these articles, and as noted by Dr. Krieg, it was not Big Pharmas, but biotech companies “on the cutting edge” (together with academic labs) that advanced the therapeutic MAb field. Big Pharmas later bought into the MAb field, typically by large acquisitions. This is especially exemplified by the acquisition of MAb drug leader Genentech by Roche.

With respect to RNAi, as mentioned above, at least Merck and Novartis among the Big Pharmas are continuing with in-house RNAi therapeutics programs. And such biotechs as Alnylam, Silence Therapeutics, Quark Phamaceuticals, Dicerna, and Santaris have RNAi and/or microRNA-based drug candidates in clinical trials, often partnered with Big Pharma companies (such as Pfizer) that have cut or reduced their own RNAi drug programs. Therefore, there are companies that are working on advancing RNAi therapeutics up the technology curve. As Dr. Krieg says in his editorial, success in such programs will be expected to lead to Big Pharma reinvestment in RNAi/microRNA therapeutics, just as in the case of MAb drugs.