PD-L1

On June 28, 2012 we published an article on this blog entitled “Cancer Immunotherapy: The Star Of The 2012 ASCO Annual Meeting”. Now comes the American Society of Clinical Oncology (ASCO) 2013 Annual Meeting, which took place from May 30 to June 3, 2013.

As in 2012, cancer immunotherapy was the star of the meeting.

In our June 2012 article, we focused on experimental monoclonal antibody (MAb) drugs that target the cell surface receptors programmed cell death-1 (PD-1) and programmed cell death-1 ligand (PD-L1). PD-1 is a member of the CD28/CTLA4 family of T cell regulators. Like CTLA4, the target of ipilimumab, PD-1 is a negative regulator of T-cell receptor signals. When PD-L1, which is a protein on the surface of some tumor cells, binds to PD-1 on T cells that recognize antigens on these tumor cells, this results in the blockage of the ability of the T cells to carry out an anti-tumor immune response. Anti-PD-1 MAb binds to PD-1 on T cells, thus preventing PD-L1 on tumor cells from binding to the PD-1 and initiating an inhibitory signal. Anti-tumor T cells are then free to initiate immune responses against the tumor cells. This mechanism of action is completely analogous to that of ipilimumab, which binds to CTLA4 and thus prevents negative signaling from that molecule.

Anti-PD-L1 therapeutics bind to PD-L1 on tumor cells. Ira Mellman (vice-president of research oncology at Genentech), believes that anti-PD-L1 might have fewer adverse effects than anti-PD-1. That is because anti-PD-L1 would target tumor cells while leaving T cells free to participate in immune networks that work to prevent autoimmune reactions.

Three experimental drugs in this area of immunotherapy were a main focus at ASCO in 2013. They are:

• BMS’ anti-PD-1 agent nivolumab (BMS-936558, MDX-1106), which we had discussed in our 2012 ASCO article.
• Merck’s anti-PD-1 agent lambrolizumab (MK-3475)
• Roche/Genentech’s anti-PD-L1 agent MPDL3280A

We shall focus on these three agents in this article.

Competition between BMS’ nivolumab and Merck’s lambrolizumab

As highlighted in the 2013 ASCO meeting and in reports by industry commentators such as FierceBiotech, there is a keen race between BMS and Merck to be the first to market an anti-PD-1 agent.

At the ASCO 2013 meeting, BMS researchers and their colleagues reported that a third of the patients in a Phase 1 trial of nivolumab saw tumors shrink at least 30%. They also reported that patients with solid tumors [metastatic melanoma, non-small cell lung cancer (NSCLC) and renal cell carcinoma (RCC)] showed high rates of 2 year overall survival–44% for melanoma, 32% for NSCLC, and 52% for RCC (clinical trial NCT00730639).

In a first Phase 1 study of a combination therapy of nivolumab with ipilimumab in metastatic melanoma, BMS researchers and their colleagues reported that the two agents could be administered in combination safely. Clinical activity for the combination therapy appeared to exceed that of published monotherapy data for each of the two agents, with greater or equal to 80% tumor reduction at 12 weeks in 30% (11/37) of patients. In addition to the ASCO 2013 presentation, the results of this combination therapy trial were published online in the New England Journal of Medicine.

According to Fierce Biotech, BMS has 6 late-stage studies under way for nivolumab, with fast-track status in place for melanoma, lung cancer and kidney cancer.

Meanwhile, Merck announced in a June 2, 2013 press release the presentation at ASCO 2013 of interim data from a Phase 1B study evaluating its anti-PD-1 agent lambrolizumab in patients with advanced melanoma. The data was presented by Antoni Ribas, M.D., Ph.D. (Jonsson Comprehensive Cancer Center, University of California, Los Angeles). in addition to the ASCO 2013 presentation, this study was published online in the New England Journal of Medicine.

A total of 135 patients with advanced melanoma were treated. Most of the adverse events seen in the study were low grade. The confirmed response rate across all dose cohorts was 38%. The highest confirmed response rate (52%) was seen in the cohort that received the highest dose (10 mg per kilogram every 2 weeks). Ten percent of the patients in the highest-dose group achieved a complete response, with response duration ranging from 28 days to 8 months.

Response rates did not differ significantly between patients who had received prior ipilimumab treatment and those who had not. Responses were durable in the majority of patients; 81% of the patients who had a response (42 out of of 52 total) were still receiving treatment at the time of analysis in March 2013. The overall median progression-free survival among the 135 patients was over 7 months.

According to Fierce Biotech, Merck now has four clinical studies under way for lambrolizumab, including a  Phase 2 trial in melanoma and Phase 1 trials in ipilimumab-naïve patients with triple-negative breast cancer, metastatic bladder cancer and head and neck cancer. The company, which has won breakthrough drug designation from the FDA for lambrolizumab, believes that the ongoing 500-patient Phase 2 melanoma study could provide enough positive data to win FDA approval. Merck is also preparing applications for late-stage clinical trials in melanoma and non-small cell lung cancer, which are planned to launch in the third quarter of 2013.

Roche/Genentech’s anti-PD-L1 agent MPDL3280A

Genentech researchers and their collaborators presented data on a clinical study of MPDL3280A in patients with metastatic melanoma at ASCO 2013. In addition to the ASCO 2013 presentation and abstract, The Angeles Clinic and Research Institute (Los Angeles, CA) published a press release about the study. Omid Hamid, M.D. of The Angeles Clinic and Research Institute made the oral presentation at the ASCO meeting.

This study was a Phase 1, multicenter, first in human, open-label, dose escalation study (clinical trial NCT01375842), which is still ongoing. It was primarily designed to assess  safety, tolerability, and pharmacokinetics of MPDL3280A in patients with metastatic melanoma. The drug was found to be well tolerated. 35 patients who began treatment at doses of 1-20 mg/kg and were enrolled prior to Jul 1, 2012 were evaluable for efficacy. An overall response rate of 26% (9/35) was observed, with all responses ongoing or improving. Some responding patients experienced tumor shrinkage within days of initial treatment. The 24-week progression-free survival was 35%. Several other patients had delayed antitumor activity after apparent tumor progression. Of three initial patients treated with a combination of MPDL3280A and vemurafenib (Daiichi Sankyo/Genentech’s Zeboraf, a targeted kinase inhibitor), two experienced tumor shrinkage, including 1 complete response. The researchers concluded that further assessment of MPDL3280A as monotherapy and combination therapy is warranted. A Phase 1 study (NCT01656642) of a combination therapy of MPDL3280A and vemurafenib in patients with previously untreated BRAFV600-mutation positive metastatic melanoma is ongoing.

Data was also presented at ASCO 2013 on the efficacy of MPDL3280A in other solid tumors. According to Roy S. Herbst, M.D. Ph.D., (Yale Cancer Center and Smilow Cancer Hospital at Yale-New Haven) MPDL3280A showed significant anti-tumor activity and was well tolerated in patients with such cancers as NSCLC, melanoma, colorectal cancer, gastric cancer, and RCC. 29 of 140 evaluable patients (21%) exhibited tumor shrinkage, with the highest overall responses in patients with NSCLC and melanoma. Of the 29 responders, 26 patients continued responding as of their last assessment.

Researchers have also been studying PD-L1 expression levels as a potential biomarker to identify likely responders. As outlined by Dr. Herbst, responses appeared to be better among patients with higher levels of PD-L1 expression. The response rate among PD-L1-positive patients was 36% (13 of 36 patients), compared with 13% (9 of 67 patients) who were PD-L1-negative. The role that PD-L1 expression might play as a biomarker is still being explored, including attempting to determine the best way to measure the protein and other related criteria.

In addition to the Phase 1 trial of MPDL3280A/vemurafenib combination therapy in melanoma, Genentech is sponsoring a Phase 1 trial of MPDL3280A in combination with bevacizumab (Genentech/Roche’s Avastin, an angiogenesis inhibitor that targets vascular endothelial growth factor) or with bevacizumab plus chemotherapy (clinical trial NCT01633970). Genentech is also sponsoring a Phase 2 clinical trial (NCT01846416) of MPDL3280A in patients With PD-L1-positive advanced NSCLC.

Conclusions

The field of immunotherapeutic MAbs for cancer, which target negative regulators of T-cell receptor signals, continues to advance. The approval and marketing of ipilimumab provides an important proof-of-principle for this approach. Now the field is advancing to include agents that target PD-1 and its negative regulator PD-L1. Studies of BMS’ PD-1 inhibitor nivolumab have advanced as far as Phase 3, and of Merck’s lambrolizumab as far as Phase 2. Meanwhile, Roche/Genentech’s PD-L1 inhibitor MPDL3280A has reached Phase 2.

However, the in terms of clinical trial data, it is still too early to meaningfully determine the efficacy of any of the PD-1 and PD-L1 inhibitor drugs. The meaningful data will come from randomized Phase 3 trials, based on overall survival rather than tumor response rate as in currently reported trials (with the exception of the Phase 1 results of clinical trial NCT00730639 of nivolumab described earlier, which included measures of overall survival).

Nevertheless, this is an extremely exciting field, and researchers, companies, and patient communities have high expectations of success.

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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 contact us by phone or e-mail. We also welcome your comments on this or any other article on this blog.

Tumor infiltrating lymphocytes (TILs) in a colorectal carcinoma. Source: Nephron. http://bit.ly/QdusBi

On April 27, 2011 we published an article on this blog entitled “Adoptive immunotherapy for metastatic melanoma?” This blog post, which was in part based on an article in the April 2011 issue of The Scientist, described a treatment for metastatic melanoma known as adoptive cell transfer (ACT), or adoptive immunotherapy. ACT is the only type of therapy that has resulted in high percentages of durable compete responses in metastatic melanoma. A durable complete response, which is tantamount to a cure, is the real desire of every cancer patient, and of their loved ones, and of caring physicians who treat them.

In ACT, a physician/researcher extracts a patient’s antigen-specific immune cells, which are usually found in tumor tissue. Such cells are known as “tumor infiltrating lymphocytes” (TILs). He or she then expands the numbers of the antitumor T lymphocytes in cell culture, using the T-cell growth factor, IL-2. The physician/researcher then infuses the cells, plus IL-2, intravenously into the patient. The infused T cells traffic to tumors and can mediate their destruction. Prior to TIL infusion, the patient may have his or her immune system temporarily ablated via “preparative lymphodepletion” with chemotherapy and sometimes also total-body irradiation. The preparative lymphodepletion treatment is associated with enhanced persistence of the transferred TILs.

In a clinical study of ACT published in 2011, the treatment resulted in the disappearance of all tumors in 20/93 patients (21.5%) with advanced metastatic melanoma. For 19 of these 20 patients (95%), the complete responses have been durable and long-lasting, in some cases lasting for over 7 years. (See also the Faculty of 1000 evaluation.)

Research on the mechanistic basis of adoptive immunotherapy, as well as on means to improve ACT technologies, is ongoing, so there is the potential to improve the durable complete response rate further. We featured a December 2012 Nature cancer immunotherapy review article that included a discussion of ways to improve ACT in the 2011 end-of-year article on our Biopharmconsortium Blog.

Despite the fact that ACT is the only type of therapy that has resulted in high percentages of durable compete responses in metastatic melanoma, it is not widely available. ACT is only available in a small number of cancer canters worldwide, and there has been little commercial interest in developing ACT.

Adoptive immunotherapies are still considered experimental, are not FDA-approved, and are not covered by third party payers. Thus only a handful of locations can bear the financial burden of administering adoptive immunotherapy. If a cancer center has a cell production facility with the required staff, the cost of producing a single dose of T-cells for adoptive transfer is approximately $20,000. ACT treatment also entails factoring in the cost of hospitalization. However, most patients only require a single dose.

The cost of ACT is, however, much lower than a full course of other immunotherapies, such as the dendritic cell vaccine Provenge (which is not indicated for melanoma) or the immunotheraputic MAb drug ipilimumab, both of which cost approximately $120,000. The total cost of a 6-month treatment with the targeted kinase drug vemurafenib is $56,400. None of these treatments result in durable complete responses, except in a very small number of patients.

The main problem with increasing the availability of ACT is the lack of a viable business model for its commercialization. Adoptive immunotherapies lack a clearly defined claim to intellectual property (IP), since the patient’s own cells are not a “drug” to be patented. It would be difficult for a private company to pursue clinical trials for FDA approval and commercialization of ACT. To conduct such trials, a company would need to build a specialized cell processing and treatment facility, with a highly trained and competent staff. If the therapies cannot be protected as IP, and would therefore not be considered proprietary, it would not be worth the effort and expense to commercialize them.

The Novartis/Penn agreement

Now comes an agreement (announced on August 6, 2012) between Novartis and the University of Pennsylvania (Penn) aimed at commercializing adoptive cellular immunotherapy.

The agreement is based on one of the improvements to ACT discussed in the December 2011 Nature cancer immunotherapy review, in which autologous T cells isolated from patient blood (not from tumors) are engineered with retroviral vectors carrying chimeric antigen receptors (CARs). This technology allows physician researchers to extend ACT beyond patients from whom TILs can be isolated and expanded. It also enables them to extend ACT beyond melanoma to include other types of solid tumors and leukemias and lymphomas. Unlike TILs, CAR-bearing T cells do not recognize surface antigens on tumor cells [presented by major histocompatibility complex (MHC) proteins] via their T-cell receptors. They instead recognize surface proteins on tumor cells via the affinity domain on the engineered CAR. This also expands the kinds of tumor cells that can be recognized, as compared to TILs.

In the Penn studies, led by David L. Porter, M.D. at the Perelman School of Medicine of the University of Pennsylvania, the researchers used this technology to treat patients with chronic lymphocytic leukemia (CLL). They designed a lentiviral vector expressing a chimeric antigen receptor with specificity for the B-cell antigen CD19, coupled with the T cell costimulatory receptor CD137 and CD3-zeta (a signal-transduction component of the T-cell antigen receptor) signaling domains. They used this vector to engineer autologous T cells, and infused the engineered cells into the patient after preparative lymphodepletion with chemotherapy. In a pilot study with one patient with refractory chronic lymphocytic leukemia (CLL), the infused cells exhibited in vivo expansion and anti-leukemia activity. The treatment resulted in complete remission, which was ongoing 10 months after initiation.

In a later study, the researchers treated three more patients with autologous engineered CAR T cells. The T cells expanded over 1000-fold in vivo, trafficked to bone marrow, and continued to express CARs at high levels for at least six months. The CAR T-cells showed anti-leukemia activity, with each engineered T cell eliminating approximately 1000 CLL cells. A CD19-specific immune response was demonstrated in the blood and bone marrow of two of three patients; these patents showed complete remission. Some of the cells in these patients persisted as memory CAR T cells and retained anti-CD19 effector activity. These results suggested that this technology has the potential to effectively treat B cell malignancies, and to induce durable complete remissions in at least a portion of patients.

As reported in August 2012, of the three patients who showed positive results with the anti-CD19 immunotherapy, two were still in complete remission over a year into the CART-19 trial, and the third patient maintained partial remission for more than seven months. An immune deficiency resulting from the treatment known as hypogammaglobulinemia, an expected chronic toxic effect of anti-B cell therapy, was corrected with infusions of intravenous immune globulin. Patients were also treated for symptoms associated with tumor lysis syndrome, an effect of tumor breakdown.

Under the agreement, Novartis acquired exclusive rights from Penn to CART-19, the investigational CAR immunotherapy that was the focus of the studies discussed earlier. The target of CART-19, CD19, is associated with several B-cell malignancies, including CLL, B-cell acute lymphocytic leukemia and diffuse large B-cell lymphoma. Novartis expects to initiate a Phase II clinical trial with CART-19 in collaboration with Penn during the fourth quarter of 2012.

To facilitate the discovery and development of additional types of CAR immunotherapy, Novartis and Penn will build the Center for Advanced Cellular Therapies (CACT) at Penn. This center will be established specifically to develop and manufacture adoptive T-cell immunotherapies under the research collaboration between Penn and Novartis.

Penn also granted Novartis an exclusive worldwide license to CARs developed through the collaboration for all indications, in addition to CART-19. In return, Novartis will provide an up-front payment, research funding, funding for the establishment of the CACT and milestone payments for the achievement of certain clinical, regulatory and commercial milestones as well as and royalties on any sales.

Business implications of the Novartis/Penn agreement

The feasibility of developing and commercializing CAR T-cell-based immunotherapy is based on the ability of Penn to patent and license its CAR technology. Such an approach in principle would apply to immunotherapies based on other types of engineered T cells, such as those engineered with retroviral vectors carrying cloned T-cell receptors, as discussed in the December 2011 Nature review article.

As discussed earlier, adoptive immunotherapies with engineered T cells would also address patients with a variety of types of cancer (not just melanoma) and from who TILs cannot be isolated. However, whether any therapies with engineered T cells can give the percentages of durable complete responses seen with TIL-based therapy of melanoma remains to be demonstrated in clinical trials.

The Novartis/Penn agreement represents an example of Novartis’ willingness to take risks, in order to “bring innovative therapies to patients”, as stated by Hervé Hoppenot, President, Novartis Oncology. Mark Fishman, President of the Novartis Institutes for BioMedical Research, sees cancer immunotherapy as “one of the exciting frontiers in cancer research,” and the CAR technology as showing “early promise as a new way for treating cancer.”

Novartis thus has not built a viable business model for TIL-based ACT. However, it is developing a parallel technology that is more protectable than TILs, which might result in bringing adoptive cellular immunotherapy to a much larger number of patients.

BiTE immunotherapy

Meanwhile another type of T-cell-based immunotherapy technology (also discussed in the Nature review) is now under development. This is bi-specific T-cell engager (BiTE) technology, originally developed by the German-American biotech company Micromet. Amgen acquired Micromet in April 2012, and is now developing the first BiTE agent, blinatumomab. Blinatumomab is a bispecific MAb that binds to CD19 on target B-cell malignancies and to CD3 (an invariant component of the T-cell receptor) on T cells. This results in the activation of the T cell to exert cytotoxic activity on the target cell. BiTE immunotherapy does not require isolation and culture of autologous T cells, and BITE technology and therapeutics derived from it are patentable as with other drugs.

In May 2012, Amgen reported that blinatumomab treatment gave a high rate (72 percent) of complete responses in a Phase 2 study in patients with relapsed or refractory B-precursor acute lymphoblastic leukemia (ALL). The rate of remission seen in this trial was a great improvement over the current standard of care. However, no durable complete responses were seen; median survival was 9 months.

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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 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.

New Alzheimer’s disease model, the CVN mouse

Our August 19, 2012 and our August 28, 2012 articles on this blog focused on the latest developments in Alzheimer’s disease (AD) drug development. To summarize the conclusions of the articles:

• The results of a new genetic study by DeCode Genetics and its collaborators strongly support the amyloid hypothesis of AD, and especially the hypothesis that reducing the β-cleavage of APP [e.g., by use of an inhibitor of β-secretase (also known as the β-site APP cleaving enzyme 1, or BACE1)] may protect against the disease.

• Nevertheless, in Phase 3 trials of two anti-amyloid monoclonal antibody (MAb) drugs in patients with mild to moderate AD–Pfizer/Janssen’s bapineuzumab (often called “bapi” for short) and Lilly’s solanezumab–the drugs failed their primary cognitive and functional endpoints.

• Roche/Genentech, as well as two academic consortia, have begun clinical trials of anti-amyloid MAb drugs in asymptomatic patients with mutations that predispose them to develop AD, or in asymptomatic patients with amyloid accumulation. These studies are based on the hypothesis that the reason for the failure of anti-amyloid MAb drugs in clinical trials has been that the patients being treated had suffered extensive, irreversible brain damage. Treating patients at a much earlier stage of disease with these agents might therefore be expected to be more successful.

Analyses of the data from the Phase 3 studies of both bapi and solanezumab will be presented in scientific meetings in October 2012. An academic research consortium will present its independent analysis of the data from the EXPEDITION studies of solanezumab at the American Neurological Association (ANA) meeting in Boston on October 8, 2012, and at the Clinical Trials on Alzheimer’s Disease (CTAD) meeting in Monte Carlo, Monaco, on October 30, 2012.

According to a September 11, 2012 news article in Drug Discovery & Development, researchers who conducted the Phase 3 trials of bapi found evidence that the drug stabilized amyloid plaque in the brain and may have ameliorated further nerve damage in patients treated with the drug. This finding is among the results to be presented in the October meetings.

Development of BACE1 inhibitors

Strictly speaking, the results of the DeCode Genetics study most strongly support the development of BACE1 inhibitors. In our August 28, 2012 article, we link to a 2010 review that includes a discussion of companies developing BACE1 inhibitors. However, we also note that the development of BACE1 inhibitors has been elusive. This is because of medicinal chemistry considerations. Specifically, it has been difficult to design a specific, high-affinity inhibitor of the BACE1 active site that can cross the blood-brain barrier and which has good drug-like ADME (absorption, distribution, metabolism and excretion) properties. Nevertheless, recently progress has been made in developing such compounds, and several companies are developing BACE1 inhibitors and have entered them into early-stage clinical trials.

Among the companies developing BACE1 inhibitors, as listed in a recent post on Derek Lowe’s In The Pipeline blog are CoMentis/Astellas, Merck, Lilly, and Takeda.

Satori Pharmaceuticals was developing γ-secretase inhibitors, but ran into safety problems

Developing γ-secretase inhibitors has been abandoned by the vast majority of companies, because of the essential role of these enzymes in the Notch pathway and other pathways involved in normal physiology. As a result, development of γ-secretase inhibitors for AD has not progressed beyond the preclinical stage.

Nevertheless, Satori Pharmaceuticals, a Cambridge, MA venture capital-backed biotech company, had been actively involved in developing γ-secretase inhibitors. Satori’s γ-secretase inhibitors were based on a proprietary scaffold derived from a compound isolated from the black cohosh plant (Actaea racemosa). The company utilized modern synthetic and medicinal chemistry to derive compounds based on this scaffold that they believed was suitable for long-term oral therapy for AD in humans. Satori’s lead compound, SPI-1865, was a potent γ-secretase modulator that decreased levels of the amyloidogenic Aβ42 peptide as well as Aβ38, increased levels of Aβ37 and Aβ39, but did not affect Aβ40. Researchers believe that decreasing Aβ42 levels in favor of shorter, less amyloidgenic A-beta forms is beneficial in treatment of AD. SPI-1865 was also selective for Aβ42 lowering over the inhibition of Notch processing, and appeared to be free of any other off-target activities.

In animal models [e.g., wild type mice and rats, and transgenic mice (Tg2576) that overexpress APP and thus have high levels of Aβ peptides] orally-administered SPI-1865 has been found to lower brain Aβ42. SPI-1865 has good brain penetration in these models, and a long half-life that should permit once a day dosing in humans.

SPI-1865 was in the preclinical stage. Satori planned to file an Investigational New Drug (IND) Application with the FDA in late 2012 with the goal of enabling initial human testing to begin in the early part of 2013.

However, in late 2012, a study in monkeys showed that Satori’s lead compound–as well as its backup compounds–disrupted adrenal function. This adverse effect was completely unexpected, and unrelated to the gamma secretase target.  As of May 30, 2013, Satori closed its doors.

Meanwhile, other companies, including Envivo Pharmaceuticals (Watertown, MA), Bristol-Myers Squibb, and Eisai continue with their R&D efforts in gamma secretase modulators for treatment of AD.

A new mouse model for AD

As Derek Lowe says in an August 31, 2012 post on “In the Pipeline” with respect to Lilly’s AD drugs, anti-amyloid MAbs, BACE1 inhibitors, and γ-secretase inhibitors are “some of the best ideas that anyone has for Alzheimer’s therapy”. Given the APP processing pathway as illustrated in the figure at the top of our August 28, 2012 article, these are the “sensible” and “logical” alternatives.

Nevertheless, there is the nagging feeling among many AD researchers that we do not understand the causes of AD, especially sporadic AD, which represents around 95% of all cases of the disease. Sporadic AD occurs in aging individuals who have normal genes for the components of the APP processing pathway. Not only do we not understand the pathobiology of sporadic AD, but we have little understanding of the normal physiological function of APP and of APP processing. Processes that may be involved in the initiation of sporadic AD may include not only those involved in Aβ production, but also those involved in Aβ clearance.

An important tool in understanding the pathobiology of AD, and potentially in developing novel therapies for the disease, would be an animal model that recapitulates the human disease as closely as possible. We published an article on AD mouse models that were designed to more closely recapitulate human AD than the most commonly used models in the September 15, 2004 issue of Genetic Engineering News. However, since the publication of our article, Carol A Colton, Ph.D. (Duke University Medical Center, Durham, NC) and her colleagues have published on their research aimed at producing an even better mouse model, known as the CVN mouse. They published their research in two articles, one in PNAS in 2006 and the other in the Journal of Neuroscience in 2008.

Charles River Laboratories (CRL) (Wilmington, MA) now offers the CVN mouse to researchers who might wish to employ it in their AD research.

Genome-wide association studies (GWAS) in humans, as well as various functional studies, have implicated variants in genes involved in inflammation and immune responses in susceptibility to late-onset, sporadic AD in humans. The Colton group, noting that commonly-used mouse models of AD recapitulated human disease very poorly, looked for differences between mice and humans in innate immunity. The biggest difference they found was that expression of nitric oxide synthase 2 (NOS2) the inducible form of nitric oxide synthase, is high in mice and low in humans. NOS2 is an enzyme that produces nitric oxide (NO), a highly reactive oxidant that can serve in signal transduction, neurotransmission and in cell killing by macrophages. Microglia, the macrophages of the brain, express NOS2 and NO. The Colton group has been studying the role of microglia and oxidants and antioxidants in microglia that can produce oxidative stress in the brain in normal aging and in AD.

Because of the striking difference in NOS2 expression between mice and humans, the Colton group created a transgenic mouse AD model by crossing mice that  expressed a mutant form of human APP known as APPSwDI (APP Swedish Dutch Iowa) with NOS2 knockout (NOS2 -/-) mice. The APPSwDI transgenic mouse, a well-characterized standard AD mouse model, was chosen because it expresses low levels of APP and high levels of Aβ peptides in the brain. The APPSwDI/NOS2 -/- mouse is the CVN mouse that is available from CRL.

Unlike APPSwDI mice and other standard AD mouse models, the CVN mouse recapitulates many features of human AD as the animals age, including AD-like amyloid pathology (starting at 6 weeks of age, which is early), perivascular deposition of amyloid, AD-like tau pathology (including aggregated hyperphosphoryated tau), AD-like neuronal loss, and reduction in interneuron numbers (including NPY interneurons). Age-related cognitive (learning and memory) loss (as assessed by the radial arm water maze test) was also seen. The researchers also saw increases in immune activation and inflammation (e.g., microglial activation) over the course of the disease; this appeared to be dependent on increases in Aβ and in tau.

The researchers also used the mouse to study changes in immune-related proteins over the course of the disease. Several protein that are encoded by genes that have been associated with sporadic AD via GWAS change over time in this mouse model, including APOE (which has been known to be important in AD for a long time) and BIN1. Other proteins that change over the course of disease include the complement component C1QB, and the centrosomal protein ninein. Immune activation genes such as those that encode IL-1α and TGF-β also show changes over the course of disease in these mice. The Colton group will soon publish their work on changes in these proteins and genes in the CVN mouse in a peer-reviewed journal.

In summary, the CVN mouse more faithfully models AD-like progression than other mouse models that have been used to study AD, including those that have been used in preclinical studies of such failed drug candidates as solanezumab, bapineuzumab, Flurizan (tarenflurbil), and Alzhemed (3-amino-1-propanesulfonic acid). It also allows researchers to study the role of genes and proteins such as those identified in GWAS studies in AD, and especially in sporadic AD. (However since the CVN mouse expresses a mutant form of APP, it can not be used to study all aspects of the pathophysiology of sporadic AD, especially the initiation of the disease process.) The CVN mouse can also be used in drug discovery and preclinical studies.

One example of such drug discovery studies is being carried out by the Colton group. They have recently been studying small APOE mimetic peptides in CVN mice. The subcutaneously administered APOE mimetics were reported to significantly improve behavior, while decreasing the inflammatory cytokine IL-6, as well as decreasing neurofibrillary tangle-like and amyloid plaque-like structures. These improvements are associated with apoE mimetic-mediated increases in protein phosphatase 2A (PP2A) activity. [Decreased PP2A levels in AD may be involved in formation of neurofibrillary tangles (NFTs) which are aggregates of hyperphosphorylated tau; PP2A may also be involved in the production of Aβ peptides. The APOE mimetic are thus potential AD therapeutics.

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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.

Macrophages attack a cancer cell

An article in the June 2012 issue of OncologyLive, authored by the publication’s senior editor, Anita T. Shaffer, reviews cancer immunotherapies now in late-stage clinical trials, and discusses the prospects for the field.

The article begins with a discussion of the recent renaissance of cancer immunotherapy, as exemplified by the April 2010 FDA approval of Dendreon’s Sipuleucel-T (APC8015, Provenge) and the March 2011 FDA approval of Ipilimumab [Medarex/Bristol-Myers Squibb’s (BMS’) Yervoy]. It then went on to discuss the exciting Phase 1 results with Medarex/BMS’ anti-PD-1 MAb, which we featured in the June 28, 2012 article on the Biopharmconsortium Blog.

But the bulk of the article was a discussion of the current late-stage (Phase 3) active immunotherapy pipeline. The article’s table lists 14 such agents. If one eliminates Cel-Sci/Teva’s Multikine (which is a mixture of cytokines), that leaves 13 agents, at least most of which can be described as therapeutic cancer vaccines. These products range from dendritic cell vaccines to tumor cell-based vaccines and viruses that encode tumor antigens.

For example, Argos Therapeutics‘ AGS-003 (Arcelis) is an autologous dendritic cell vaccine loaded with the patient’s own messenger RNA (mRNA). This vaccine is in Phase 3 clinical trials in patients with newly diagnosed metastatic renal cell carcinoma (mRCC). We mentioned Argos and its technology in our November 25, 2011 article on the late Ralph Steinman, MD, who had discovered the dendritic cell and elucidated its central role in the immune system. Dr. Steinman was a cofounder of Argos. Patient mRNA in Argos’ cellular immunotherapy product encode tumor antigens, which are expressed on the surface of the dendritic cells. The dendritic cells then potentiate the production of tumor antigen-specific T cells which attack the patient’s tumor.

According to a July 2 2012 company news release, AGS-003 is a fully personalized immunotherapy that preferentially targets mutated tumor antigens, which drive disease progression. Patient T cells recognize these antigens as foreign. This enables AGS-003 to direct a specific and potent anti-tumor immune response, without attacking normal tissues.

In a Phase 2 study of a combination of AGS-003 and sunitinib (Pfizer’s Sutent, the standard of care for mRCC), researchers demonstrated a statistically significant correlation between the number of anti-tumor T cells induced and overall survival in mRCC patients receiving AGS-003. Adding AGS-003 to sunitinib doubled overall survival for these patients compared to historical results for unfavorable risk patients treated with sunitinib alone. Over 50 percent of patients in the study survived longer than 30 months after initiating therapy, which is four times the expected rate for sunitinib.

Another type of cancer vaccine is based on modified cancer cells. In our Steinman article, this strategy is represented by BioSante’s GVAX cancer vaccines [now licensed by Aduro BioTech (Berkeley, CA)]. One such vaccine, GVAX Pancreas for pancreatic cancer (which is now in clinical trials) is based on human pancreatic cancer cell lines that have been engineered to secrete the immunostimulant granulocyte-macrophage colony-stimulating factor (GM-CSF), and have then been lethally irradiated. Since the most advanced GVAX products are in Phase 1 and Phase 2 clinical trials, GVAX was not covered in the OncologyLive article.

However, other more advanced immunotherapies, such as NewLink Genetics‘ HyperAcute Pancreas cancer immunotherapy (in Phase 3 trials), also consist of modified cancer cells. HyperAcute Pancreas consists of equal parts of two separate allogeneic pancreatic cancer cell lines engineered to express α-galactosidase (an enzyme that is not expressed by natural human pancreatic tumors).

Another type of cancer vaccine is based on viruses that encode tumor antigens. For example, Bavarian Nordic A/S’ PROSTVAC, a treatment for prostate cancer, is a  sequentially dosed combination of vaccinia and fowlpox poxviruses that encode an altered, more immunogenic form of prostate-specific antigen (PSA) plus three immune enhancing costimulatory molecules ( B7.1, ICAM-1, and Lfa-3).

The late-stage immunotherapies listed in the table in the OncologyLive article include cancer vaccines that represent several design strategies other than the three mentioned here.

Some good news about sipuleucel-T

The OncologyLive article also referred to an abstract presented at the 2012 American Society of Clinical Oncology (ASCO) meeting, which suggests that the survival advantage for prostate cancer patients treated with sipuleucel-T was significantly greater than the 4.1-month benefit reported in the Phase 3 trial that led to approval of the agent. The analysis reported in this abstract indicates that the overall survival treatment benefit with sipilleucel-T ranged from 4.1 months to  7.8 months.

Conclusions

As illustrated by the number of late-stage cancer immunotherapies in development, as well as the approval of two drugs in 2010 and 2011, cancer immunotherapy is here to stay. One question in the use of such immunotherapies, as highlighted in the OncologyLive article, is how they will be integrated with such established modalities as cytotoxic chemotherapy, radiation therapy, and targeted cancer therapies.

Another factor is cost. A course of treatment with sipuleucel-T costs $93,000, and the cost of a course of treatment with ipilimumab is $120,000. However, as pointed out in the OncologyLive article, the total cost of treatment with other modalities that may continue for months or years may be higher. Nevertheless, the cost of cancer therapies, especially those that only increase overall survival by a few months, is a great concern to patients, physicians, and payers.

It must be remembered, however, that nearly all cancer therapies, when first introduced to the market, gave only slightly enhanced survival over older treatments. However, as oncologists learned how to use the therapies better (e.g., with changes in dosing, use in other groups of cancer patients, and/or use in combination therapies), numerous therapies eventually gave long-term remissions or even cures and proved to be cost-effective indeed.

Another issue with the cancer immunotherapy field, as pointed out in the OncologyLive article, is the difficulty of raising capital for cancer immunotherapy specialty companies. This is especially true in the current market, where most biotech companies have difficulty in raising capital. However, what venture capitalists and Big Pharma consider to be “premature technologies” or “unproven” emerging early-stage areas, as is usually the case, have particular difficulty in attracting investment.

Nevertheless, if and when additional late-stage cancer immunotherapy agents successfully complete Phase 3 trials and gain approval, this may demonstrate to investors that cancer immunotherapy has graduated from the premature-technology stage. In that case, cancer immunotherapy specialty companies may find it easier to attract capital, and large pharmaceutical companies may wish to acquire some of these companies. Since Big Pharma already is involved in developing such immunotherapies as anti-PD-1 and anti PD-1L, and ipilimumab is already a marketed Big Pharma drug, that should not be much of a stretch.

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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.

The American Society of Clinical Oncology (ASCO) held its 2012 Annual Meeting on June 1-5, 2012. Arguably the highlight of the meeting was the June 2, 2012 presentation by Bristol-Myers Squibb (BMS) on its Phase 1 immunotherapeutic, anti-PD-1 (BMS-936558). The results of this study were also published ahead of print on June 2, in the online version of the New England Journal of Medicine. Nature published a “News in Focus” article on the same subject by Nature staff writer Erika Check Hayden in its 6 June issue.

BMS acquired its anti-PD-1 MAb product BMS-936558 (MDX-1106) via its 2009 acquisition of Medarex. This is the same way in which BMS acquired its now-marketed immunotherapy, ipilimumab (Yervoy), which was approved by the FDA in March 2011. Both BMS-936558 and ipilimumab are monoclonal antibodies (MAbs). Ono Pharmaceuticals has been a partner in the development of anti-PD-1 MAb since its original collaboration with Medarex; Ono retains the right to exclusively develop and market the agent (which is also designated as ONO-4538) in Japan, Korea and Taiwan.

PD-1 (“programmed cell death-1”) is a receptor on the surface of activated T lymphocytes of the immune system. PD-1 is a member of the CD28/CTLA4 family of T cell regulators. Like CTLA4, the target of ipilimumab, PD-1 is a negative regulator of T-cell receptor signals. When a protein on the surface of some tumor cells, known as PD-1 ligand (PD-L1), binds to PD-1 on T cells that recognize antigens on these tumors cells, this results in the blockage of the ability of the T cells to carry out an anti-tumor immune response. Anti-PD-1 MAb binds to PD-1 on T cells, thus preventing PD-L1 on tumor cells from binding to the PD-1 and initiating an inhibitory signal. Anti-tumor T cells are then free to initiate immune responses against the tumor cells. This mechanism of action is completely analogous to that of ipilimumab, which binds to CTLA4 and thus prevents negative signaling from that molecule.

Phase 1 clinical study of Medarex/BMS’s anti-PD-1

The Phase 1 clinical study was carried out by a multi-institution team of investigators, led by Suzanne L. Topalian, M.D. (Johns Hopkins University School of Medicine, Baltimore, MD.) The researchers enrolled patients with advanced melanoma, non-small-cell lung cancer (NSCLC), prostate cancer, renal cell cancer (RCC), or colorectal cancer. Patients received anti-PD-1 at a dose between 0.1 and 10.0 milligrams per kilogram of body weight every two weeks. Tumor response was determined after each 8-week treatment cycle. Patients received up to 12 cycles of treatment until either unacceptable adverse events, disease progression or a complete response occurred. A total of 296 patients received treatment through February 24, 2012.

Among the 236 patients in whom tumor responses could be evaluated, objective responses were observed in patients with NSCLC, melanoma, or RCC. Cumulative response rates (among patients treated with all doses of anti-PD-1) were 18% among patients with NSCLC, 28% among patients with melanoma, and 27% among patients with RCC.  These responses were durable–20 of 31 responses lasted 1 year or more in patients with 1 year or more of follow-up. Anti–PD-1 produced objective responses in approximately one in four to one in five patients with NSCLC, melanoma, or RCC.

In addition to patients with objective responses, other patients treated with anti-PD-1 exhibited stable disease lasting 24 weeks or more–5 patients (7%) with NSCLC, 6 patients (6%) with melanoma, and 9 patients (27%) with RCC.

Significant drug-related adverse effects were seen in 11% of the patients, including three deaths due to pulmonary toxicity. In most cases, adverse effects were reversible, and the observed adverse-event profile does not appear to preclude the use of the drug. A maximum tolerated dose was not reached in this study.

The exciting finding of this study is that anti-PD-1 produced durable responses not only in melanoma and RCC (the two types of cancer that are deemed to be “immunogenic”), but also in NSCLC, a much more common cancer that kills more people per year than any other cancer. Moreover, response rates with anti-PD-1 were much higher that those achieved with the other recently approved immunotherapeutics. In the Phase 3 clinical trial of ipilimumab that led to its approval, this drug gave response rates of 11% in melanoma patients. The other recently approved immunotherapeutic, the prostate cancer-specific dendritic cell vaccine Sipuleucel-T (Dendreon’s Provenge, APC8015), gives very low response rates and no complete responses. According to Antoni Ribas (Jonsson Comp­rehensive Cancer Center, University of California, Los Angeles CA) as quoted Ms. Hayden’s Nature “News in Focus” review, if an immunotherapy “breaks the 10% ceiling” as did anti-PD-1, it becomes “even more important and clinically relevant”.

Despite the exciting efficacy results with anti-PD-1, and despite the fact that it was deemed that the adverse-event profile did not appear to preclude the use of the drug, researchers would still like to get away from the serious adverse effects (including three deaths) seen with anti-PD-1. As with other immunotherapeutics (e.g., ipilimumab), researchers hypothesize that anti-PD-1’s serious adverse effects were due to autoimmune responses.

Phase 1 clinical study of Medarex/BMS’ anti-PD-L1

A potential way of achieving similar efficacy to anti-PD-1 with an improved safety profile is provided by another Phase 1 immunotherapeutic,  anti-PD-L1. Anti-PD-L1 MAb drugs are being developed by Medarex/BMS, Roche/Genentech, and other companies. As mentioned earlier, PD-L1 is the binding partner of PD-1 that is expressed on some tumor cells. As quoted in the Nature “News in Focus” review, Ira Mellman (vice-president of research oncology at Genentech), believes that anti-PD-L1 might have fewer adverse effects than anti-PD-1. That is because anti-PD-L1 would target tumor cells while leaving T cells free to participate in immune networks that work to prevent autoimmune reactions.

The results of a Phase 1 clinical study of BMS/Medarex’ anti-PD-L1 (also known as MDX-1105) were also published ahead of print in the online version of the New England Journal of Medicine on June 2, 2012; this was a “companion study” to the Phase 1 study of anti-PD-1. This study was also carried out by a multi-institution team of investigators, led by Julie R. Brahmer, M.D. (Johns Hopkins University School of Medicine, Baltimore, MD.); Dr. Topalian, among other investigators on the anti-PD-1 trial, also participated in the study.

This Phase 1 trial was a dose escalation study that was carried out via a similar protocol to the anti-PD-1 trial discussed earlier. As of February 24, 2012, a total of 207 patients — 75 with NSCLC, 55 with melanoma, 18 with colorectal cancer, 17 with RCC, 17 with ovarian cancer, 14 with pancreatic cancer, 7 with gastric cancer, and 4 with breast cancer — had received anti–PD-L1 antibody, for a median duration of 12 weeks. Among patients with an evaluable response, an objective response (i.e., a complete or partial response) was seen in 17% of patients with melanoma, 12% of patients with RCC, 10% of patients with NSCLC, and 6% of patients with ovarian cancer. Responses lasted for 1 year or more in 8 of 16 patients with at least 1 year of follow-up. Prolonged disease stabilization was seen in 12-41% of patients with advanced cancers, including NSCLC, melanoma, and RCC.

Significant drug-related adverse effects were seen in 9% of patients.

Although the two agents were not compared directly in a randomized trial, the frequency of objective responses for anti–PD-L1 MAb appears to be somewhat lower than that observed for anti–PD-1 MAb in initial Phase 1 trials; the frequency and severity of significant drug-related adverse events also appears to be lower. However, whether these differences will hold up in Phase 2 and 3 clinical trials remains to be determined. The clinically appropriate dose of anti–PD-L1 will also require further definition later studies. Nevertheless, the Phase 1 trial showed that anti-PD-L1 MAb induced durable tumor regression (objective response rate of 6-17%) and prolonged disease stabilization (rate of 12-41% at 24 weeks) in patients with select advanced cancers, including NSCLC, a tumor type that had been deemed to be “non-immunogenic”. This is essentially the same result that was observed for anti-PD-1MAb.

A predictive biomarker for treatment with anti-PD-1?

As with other modes of cancer therapy, it would be very useful to have mechanism-based predictive biomarkers to identify appropriate candidates for treatment with anti-PD-1 or anti-PD-L1 immunotherapy. The findings of the Phase 1 anti-PD-1 study suggest that PD-L1 expression in tumors is a candidate biomarker that warrants further evaluation for use in selecting patients for immunotherapy with anti–PD-1 MAb. The researchers found that 36% of patients with PD-L1–positive tumors achieved an objective response, while no patients with PD-L1–negative tumors achieved such a response. These results suggest that PD-L1 expression on the surface of tumor cells in pre-treatment tumor specimens may be associated with an objective response. However, further studies will be necessary to define the role of PD-L1 as a predictive biomarker of response to anti–PD-1 therapy. Similarly, it appears reasonable that tumor expression of PD-L1 may be a predictive biomarker of response to anti-PD-L1 therapy. However, this hypothesis must also be tested in further clinical studies.

Further studies of anti-PD-1 MAb

Two studies of BMS-936558/MDX-1106 anti–PD-1 MAb, both in advanced/metastatic clear-cell RCC, are now recruiting patients. One trial is a Phase 1 biomarker study involving immunologic and tumor marker correlates of efficacy (progression-free survival and tumor response). The other trial is a Phase 2 efficacy (progression-free survival and tumor response) study; this is a dose ranging study that is designed to determine if a dose response exists. Phase 3 studies of BMS-936558/MDX-1106 anti–PD-1 MAb for the treatment of non–small-cell lung cancer, melanoma, and renal-cell cancer are also being planned.

Conclusions

The exciting results of the studies with BMS’ anti-PD-1 and anti-PD-L1 have only been in Phase 1 studies. Thus caution is advisable in interpreting these results, pending the results of further clinical studies. Nevertheless, these results, together with the recent approval of ipilimumab (Medarex/Bristol-Myers Squibb’s Yervoy) and of Sipuleucel-T (Dendreon’s Provenge), indicate that cancer immunotherapy, a field that not so long ago was regarded as an impractical dream, is very much alive and well. In addition to clinical development and approval of immunotherapeutic agents, exciting basic and drug discovery research in this field is ongoing. This was recognized by the awarding of the 2011 Nobel Prize in Physiology or Medicine for research with profound implications for the development of cancer immunotherapies.

The Biopharmconsortium Blog has been covering new developments in cancer immunotherapy since the spring of 2011. Our earlier articles on this subject (with links) are listed in our December 31, 2011 article, entitled “Read the cancer immunotherapy review in the 22 December 2011 issue of Nature!”

Cancer immunotherapy represents one of several “scientifically premature” or “frontier science” areas discussed in this blog that are providing new opportunities for drug discovery and development–for young entrepreneurial biotech start-ups and for more established biotechnology and pharmaceutical companies. Corporate strategists would do well to explore such areas for potential new R&D programs for their companies.

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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.