An exciting new study on Alzheimer’s disease (AD) was published in the 2 August issue of Nature. The study was carried out by researchers at deCode Genetics (Reykjavik Iceland) and their collaborators at Genentech and several academic institutions. A News and Views article by leading AD researcher Bart De Strooper and genomics researcher Thierry Voet (both at KU Leuven, Leuven, Belgium) analyzes this study and its implications.

Amyloid plaques are a central feature of AD.  They largely consist of amyloid-β (Aβ) peptides. Aβ peptides are formed via sequential proteolytic processing of the amyloid precursor protein (APP), catalyzed by two aspartyl protease enzymes–β-secretase and γ-secretase.  The β-site APP cleaving enzyme 1 (BACE1) cleaves APP predominantly at a unique site. However, γ-secretase cleaves the resulting carboxy-terminal fragment at several sites, with preference for positions 40 and 42. This leads to formation of amyloid-β1–40 (Aβ40) and Aβ1–42 (Aβ42) peptides. APP processing to yield Aβ peptides is illustrated by the figure at the top of this article.

By studying rare, familial cases of early-onset AD, human geneticists have identified three disease genes in these conditions— genes for APP, and for two presenilins, PS1 and PS2. The presenilins are components of γ-secretase, which exists as an intramembrane protease complex. Mainly because of these genetic studies, as well as studies in animal models and postmortem studies of AD brains, the majority of AD researchers have focused on the APP processing pathway and/or on aggregation of Aβ to form plaques as intervention points for therapeutic strategies. The hypothesis that this is the central AD disease pathway is called the “amyloid hypothesis”.

Up until the publication of the new deCode report, of the 30-odd coding mutations in APP that have been found, around 25 are pathogenic, usually resulting in autosomal dominant early-onset Alzheimer’s disease. Coding mutations at or near the β- or γ-proteolytic sites have appeared to result in overproduction of either total Aβ or a shift in the Aβ40:Aβ42 ratio towards formation of Aβ42, which is the more toxic of the two Aβ peptide. Until now, mutations in APP have not been implicated in the common, late-onset form of Alzheimer’s disease.

In the new deCode study, the researchers studied coding variants in APP in a set of whole-genome sequence data from 1,795 Icelanders. They identified a single nucleotide polymorphism (SNP), designated as rs63750847. The A allele of this SNP (rs63750847-A) results in an alanine to threonine substitution at position 673 in APP (A673T). The A673T mutation was found to be significantly more common in the elderly (age 85-100) control group (i.e., those without AD) than in the AD group. The researchers therefore concluded that the mutation is protective against AD.

The researchers also found that in a cohort of individuals over 80, those who were heterozygous for the A673T mutation performed better in a test of mental capacity than did control subjects. The authors concluded that the A673T mutation not only protects against AD, but also against the mild cognitive decline that is normally associated with old age.

In cellular studies (i.e., studies in cultured cells transfected with genes coding for wild type or mutant APP) and in biochemical studies, the researchers found that APP carrying the A673T mutation undergoes about 40% less cleavage by BACE1 than does wild-type APP, resulting in 40% less production of both Aβ40 and Aβ42.

The researchers conclude that the strong protective effect of the A673T mutation against AD provides proof of principle for the hypothesis that reducing the β-cleavage of APP (e.g., by use of BACE1 inhibitors, such as those being  developed by some pharmaceutical companies) may protect against the disease. (However, success in developing BACE1 inhibitors has been elusive.) Moreover, since the A673T allele also protects against cognitive decline in elderly individuals who do not have AD, AD and age-related mild cognitive decline may be mediated through the same or similar mechanisms.

Despite this compelling genetic finding, amyloid pathway-targeting drugs have not shown efficacy in Phase 3 trials

In our January 26, 2010 blog article, we discussed Phase 2 clinical trials of bapineuzumab, a monoclonal antibody (MAb) drug that is specific for Aβ, in mild to moderate AD. In that article, we referred to the drug as “Elan/Wyeth’s bapineuzumab”, after the original developers of the drug. As the result of mergers and acquisitions, the drug is now referred to as “Pfizer/Janssen’s bapineuzumab”. Many commentators call it “bapi” for short.

As we discussed in that article, the overall result of the Phase 2 trial was that there was no difference in cognitive function between patients in the bapi-treated and the placebo groups. However, the study did not have sufficient statistical power to exclude the possibility that there was such a difference. Retrospective analysis of the data from the trial suggested that bapi-treated patients who were not carriers of the apolipoprotein E epsilon4 allele (ApoE4) showed improved cognitive function as compared to placebo treatment. Given that this conclusion was reached via retrospective analysis, the idea that the bapi was efficacious in ApoE4 noncarriers was only a hypothesis, which would require prospective clinical trials to confirm. Janssen and Pfizer had been conducted large Phase 3 trials of bapi, which they prospectively segregated into ApoE4 carrier and noncarrier groups in order to test this hypothesis.

As of the past several weeks, the results of these Phase 3 trials have come in. On July 23rd, 2012, Pfizer announced the top-line results of an 18-month Janssen-led Phase 3 study of intravenous bapi in approximately 1,100 patients with mild to moderate Alzheimer’s disease who carry at least one ApoE4 allele. The drug failed to meet its co-primary endpoints (change in cognitive and functional performance compared to placebo) in that study. On August 6, 2012, Pfizer announced the top-line results of the corresponding Phase 3 study of intravenous bapi in patients with mild-to-moderate Alzheimer’s disease who do not carry the ApoE4 genotype. Once again, the co-primary clinical endpoints were not met. Based on these results, the companies decided to discontinue all other intravenous bapi studies in patients with mild-to-moderate Alzheimer’s disease.

The bapi development program continues a history of amyloid pathway-targeting drugs that were taken into Phase 3 trials despite Phase 2 results that showed no statistically significant efficacy. For example, we cited the cases of Myriad Pharmaceuticals’ Flurizan (tarenflurbil) and Neurochem’s (now Bellus Health) Alzhemed (3-amino-1-propanesulfonic acid) in our January 26, 2010 blog article.

Leading industry commentator Matthew Herper of Forbes referred to the failure of bapi as “the latest piece of evidence of the drug industry’s strange gambling problem.” Johnson & Johnson (the parent company of Janssen) spent more than $1 billion to invest in Elan and get one-quarter of bapi, and Wyeth (later Pfizer) and Elan put the drug into Phase 3, despite the Phase 2 failure of bapi.

The temptation for pharmaceutical companies to take a chance on an AD drug such as bapi, Flurizan, and Alzhemed is driven by the complete lack of disease-modifying AD drugs, and the thinking that even a not-very-effective drug that receives FDA approval might generate billions of dollars in annual sales. In the case of bapi there was also that tantalizing suggestion that bapi might show efficacy in the subset of patients who lacked ApoE4.

In an August 16, 2012 article in Forbes, Dr. John LaMattina (the former President of Pfizer Global R&D) engages in informed speculation as to why bapi was moved into Phase 3. Dr. LaMattina (in contrast to critics like Mr. Herper, who discounted the ApoE4 retrospective analysis as “data-dredging” that was “likely to be due to chance”) referred to the efficacy signal of the Phase 2 trials as “mixed” due to the ApoE4 analysis. He stated that such “mixed results” present an “agonizing” dilemma for a pharmaceutical company.

In deciding whether to go forward Phase 3 trials of bapi, Dr. LaMattina further speculates that the decision might have been influenced by stakeholders such as AD patient advocates, and scientists who strongly believed in the science behind bapi, especially the amyloid hypothesis. Moreover, bapi had been shown to be relatively safe. In addition, dropping bapi would have caused public relations damage. Dr. LaMattina concludes, based on this analysis, “…this was a situation where these companies were in possession of a relatively safe drug, with a modest chance of success in being efficacious in what may be the biggest scourge that society will face.  How can you not make this investment?” He reminds us that pharmaceutical R&D “is a high risk, high reward business”.

Nevertheless, bapi joined Flurizan and Alzhemed on the list of high-profile amyloid-pathway failures. Now a Phase 3 trial of Lilly’s solanezumab, another MAb drug that targets Aβ, is nearing completion, with the results expected in September. Published Phase 2 results were designed to test safety, not efficacy, and 12 weeks of drug treatment gave no change in cognitive function. Although the results of the Phase 3 trial will not be known until they are reported, analysts expect the drug to fail because of its similarity to bapi.

Why don’t amyloid pathway-targeting drugs show efficacy in clinical trials, despite the compelling genetic evidence for the amyloid hypothesis?

The almost standard answer to that question given by scientists and clinicians who support the amyloid hypothesis is that we have been testing the drugs too late in the course of AD progression, after the damage to the brain has become irreversible. Roche/Genentech is testing this idea in its clinical trials of its drug candidate crenezumab (licensed from AC Immune), which is yet another MAb drug that targets Aβ. In a 5-year Phase 2a clinical trial, Genentech is testing intravenous crenezumab in 300 cognitively healthy individuals from a large Colombian kindred who harbor the Glu280Ala (codon 280 Glu to Ala substitution) PS1 mutation. This mutation causes dominant early−onset familial AD, and is associated with increased levels of Aβ42 in plasma, skin fibroblasts, and the brain. Family members with this mutation begin showing cognitive impairment around age 45, and full dementia around age 51.

Genentech is conducting this trial in collaboration with the Banner Alzheimer’s Institute and the National Institutes of Health. The company says that this trial is the first-ever AD prevention study in cognitively healthy individuals. Genentech further says that the trial may help to determine if the amyloid hypothesis is correct–more specifically, it may help to determine if a drug that works by depleting amyloid plaques can be effective in preventing and/or treating AD.

Moreover, Genentech states that there is significant unmet medical need within this Colombian population. This large extended family may have as many as 5,000 living members, and no other population in the world offers a sufficiently large number of mutation carriers close to the age of potential disease onset for a study to determine whether a prevention treatment may work. This effort by Genentech thus represents an application of a rare disease strategy to AD.

It is also possible, however that drugs that work by lowering levels of Aβ will not be efficacious in treating AD, even if administered early in the disease process. This may be true despite the findings of the new genetic study by the deCode Genetics group. For example, in their Nature News and Views article, Drs. De Strooper and Voet remind us that if the A673T mutation indeed works via lowering of Aβ levels, it works via lifelong lowering of Aβ, not lowering of Aβ in patients who already have AD, as in all clinical trials so far of anti-Aβ antibodies. (Even Genentech’s Colombian trial may involve lowering of Aβ levels relatively late in the course of exposure of patients to a disease process that will result in AD.)

Moreover, as these authors speculate on the basis of work on another mutation at the same site in the APP protein, it is possible that the protective effect of the A673T mutation may be due to changing the aggregation properties of Aβ peptides, resulting in a less-toxic form of Aβ. If true, this would mean that the protective effect of the A673T mutation is due to qualitative, rather than quantitative changes in Aβ. In that case, the finding of protection from AD by the A673T mutation might not be as predictive of the efficacy of such Aβ-lowering treatments as the use of anti-Aβ MAb drugs as drug developers might like.
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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.

 

Two previous articles on this blog have included discussions of the “co-clinical mouse/human trial” strategy for improving mouse models of human cancer, and simultaneously improving human clinical trials of drugs for these cancers. Now comes an article on the use of a co-clinical trial strategy in personalized treatment of non-small cell lung cancer (NSCLC) in the 29 March 2012 issue of Nature. In the same issue of Nature is a News and Views article by Genentech’s Leisa Johnson Ph.D. that provides a minireview of the research article.

As we discussed in our April 15, 2010 article on this blog, the co-clinical trial strategy has been 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.

As discussed in that article, these researchers constructed genetically engineered transgenic mouse strains that have genetic changes that mimic those found in human cancers. These mouse models spontaneous develop cancers that resemble the corresponding human cancers. In Dr. Pandolfi’s  ongoing co-clinical mouse/human trial project, researchers simultaneously 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 of this two-year project 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 human clinical trials being “shadowed” by simultaneous studies in mice included Phase 3 trials of several targeted therapies for lung and prostate cancer. Xenograft models in which tumor tissue from the patients had been transplanted into immunosuppressed mice were also being tested in parallel with the genetically engineered mouse models. This project represents the most rigorous test to date of how well genetically engineered mouse models of cancer can predict clinical outcomes.

Our October 28, 2011 blog article, which is mainly a review of a 29 September 2011 Nature article by Nature writer Heidi Ledford, Ph.D., focuses on ways to fix the clinical trial system. Our article includes a discussion of a co-clinical trial 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 had an intact PTEN gene and the other of which was PTEN deficient. In this trial, researchers tested the Akt inhibitor perifosine (Keryx Biopharmaceuticals, an alkylphospholipid) and the mTOR inhibitor CCI-779 (temsirolimus; Pfizer’s Torisel), both alone and in combination, in vitro and in vivo. 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 in 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.

The new co-clinical trial reported in the March 2012 issue of Nature

The March 2012 Nature report describes research carried out by a large, multi-institution academic consortium, which included Dr. Pandolfi. It focuses on strategies for treatment of patients with non-small-cell lung cancer (NSCLC) with activating mutations in KRAS (Kirsten rat sarcoma viral oncogene homolog). These mutations occur in 20–30% of NSCLC cases, and patients whose tumors carry KRAS driver mutations have a poor prognosis. Moreover, KRAS is a “hard” or “undruggable” target, and no researchers have thus been able to discover inhibitors of oncogenic KRAS.

Because of the intractability of oncogenic KRAS as a target, researchers have been attempting to develop combination therapies for mutant-KRAS tumors (including, for example, colorectal cancers as well as NSCLCs) that address downstream pathways controlled by KRAS. We discussed examples of these strategies in our book-length report Multitargeted Therapies: Promiscuous Drugs and Combination Therapies, published by Cambridge Healthtech Institute/Insight Pharma Reports in 2011. Strategies discussed in that report are based on the finding that KRAS controls signal transduction via two key pathways: the B-Raf-MEK-ERK pathway and the PI3K-Akt pathway. This is illustrated in the figure at the top of this article. As discussed in our 2011 report, researchers are attempting to develop treatments of mutant-KRAS tumors that involve combination therapies with an inhibitor of the mitogen-activated protein kinase (MEK) together with an inhibitor of phosphatidylinositol 3-kinase (PI3K). Researchers are also attempting to develop combination therapies of MEK inhibitors with standard cytotoxic chemotherapies, which if successful will avoid having to use combinations of two expensive targeted therapies.

In the co-clinical trial that is the focus of the 29 March 2012 Nature research report and News and Views commentary, researchers developed a genetically-engineered mouse model to study treatment of mutant-KRAS NSCLCs with either the antimitotic chemotherapy drug docetaxel alone, or docetaxel in combination with the MEK kinase inhibitor selumetinib (AZD6244, AstraZeneca). In the parallel human clinical trial, researchers are also studying treatment of patients with mutant-KRAS NSCLC with docetaxel alone or docetaxel plus selumetinib. (There is no treatment arm in the human clinical trial in which patients are treated with selumetinib alone, since selumetinib monotherapy of NSCLC patients had shown no efficacy in a previous Phase 2 study; this was confirmed in mouse model studies.)

In humans with mutant-KRAS NSCLC, many tumors with mutations in KRAS have concomitant genetic alterations in other genes that may affect response to therapy. Therefore, the co-clinical trial researchers wished to design mouse models with lung tumors with either Kras mutations alone or with mutations in both Kras and another gene that is often concomitantly mutated in mutant-KRAS NSCLCs in humans. The researchers therefore constructed mouse models with cancers bearing the activating Kras(G12D) mutation, either alone or together with an inactivating mutation in either p53 or Lkb1. The researchers achieved this via a conditional mutation system using nasal instillation of specifically genetically-engineered adenoviruses. As result, a small percentage of lung epithelial cells harbored these mutations. It is from these cells that the NSCLC-like tumors arose, analogous to the clonal origin of sporadic lung tumors in humans.

Of the two tumor suppressor genes that are frequently mutated in human mutant-KRAS NSCLCs and that were modeled by the co-clinical trial researchers, p53, often called the “guardian of the genome”, is familiar to most of you. The other gene, Lkb1 [liver kinase B1, also known as serine/threonine kinase 11 (STK11)], was discussed in an earlier article on the Biopharmconsortium Blog, entitled “The great metformin mystery–genomics, diabetes, and cancer.”

LKB1 (whether in regulation of gluconeogenesis in the liver or in its role as a tumor suppressor) acts by activation of AMPK (AMP-activated kinase, a sensor of intracellular energy status.) In lung cancer (as shown by the same group that performed the 2012 co-clinical trial), LKB1 acts to modulate lung cancer differentiation and metastasis.  Germline mutations in LKB1 are associated with the familial disease Peutz-Jegher syndrome, in which patients develop benign polyps in the gastrointestinal tract. Studying a mouse model of mutant-LKB1 Peutz-Jeger syndrome, Reuben J. Shaw (Howard Hughes Medical Institute, The Salk Institute for Biological Studies, La Jolla, CA, who was prominently mentioned in our “great metformin mystery” article) and his colleagues showed that the LKB1-AMPK pathway downregulates the mTOR pathway–specifically the rapamycin-sensitive mTOR complex 1 (mTORC1) and its downstream effector hypoxia-inducible factor-1α (HIF-1α). HIF-1α expression in turn upregulates the expression of its downstream effectors hexokinase II and glucose transporter 1 (GLUT1), which are involved in cellular utilization of glucose. LKB1-deficient polyps in this mouse model thus show increased expression of hexokinase II and GLUT1, resulting in dramatically increased glucose utilization.

In the new co-clinical trial, genetically-engineered mice that showed established lung tumors [as determined via magnetic resonance imaging (MRI)] were randomized to receive either docetaxel, selumetinib, or a combination of the two drugs. For tumors with only a Kras mutation, treatment with docetaxel alone resulted in a modest rate of response, with 30% of mice showing a partial response. Mice that bore mutant-Kras tumors that also had mutations in either p53 or Lkb1 had much lower rates of response to docetaxel monotherapy (5% and 0%, respectively), and more of these mice showed progressive disease on MRI or died of their disease. Of mice treated with the docetaxel/selumetinib combination, those with single-mutant Kras tumors showed a 92% overall response rate, and those with mutant Kras/p53 tumors showed a 61% overall response rate. However, mice with mutant Kras/Lkb1 cancers showed only a modest response to the docetaxel/selumetinib combination; 33% of mice achieved a partial response. The difference in response rate of mice with Kras/Lkb1 tumors to docetaxel/selumetinib compared to the other two genotypes was found to be statistically significant.

Using the genetically-engineered NSCLC mouse model in biomarker development

In human patients in clinical trials or in treatment for their cancers, performing repeated biopsies to monitor treatment is difficult. The co-clinical trial researchers therefore wished to develop less invasive means of monitoring both co-clinical and clinical trials of docetaxel/selumetinib treatment of NSCLC. They therefore tested the use of positron emission tomography (PET) with 18F-fluoro-2-deoxyglucose (FDG-PET) as an indicator of early response to therapy that could be used in the clinic.  Prior to its radioactive decay (109.8 minute half -life), 18F-FDG is a nonmetabolizable glucose analogue that moves into cells that is preferentially taken up by high-glucose utilizing cells. The researchers found that both Kras/p53 and Kras/Lkb1 tumors showed higher FDG uptake in vivo in the mouse model than did single-mutant Kras tumors. As expected from the earlier study, GLUT1 expression was elevated in Kras/Lkb1 mutant tumors. In human patients, pre-treatment, mutant KRAS/LKB1 tumors also showed a higher FDG uptake that did KRAS tumors negative for LKB1.

Treatment of the mice with docetaxel alone gave no significant changes in FDG uptake in Kras, Kras/p53, or Kras/Lkb1 tumors in vivo. However, within 24 hours of the first dosing of docetaxel/selumetinib, FDG uptake was markedly inhibited in Kras and Kras/p53 tumors. In contrast, treatment of mice with Kras/Lkb1 mutant tumors gave no appreciable decrease in FDG uptake in these tumors. These results show that early changes in tumor metabolism, as assessed by FDG-PET, predict antitumor efficacy of docetaxel/selumetinib treatment.

The FDG-PET study in this mouse model supports the use of this imaging method as a biomarker to monitor the course of treatment in humans.

Cellular signaling in mutant Kras, Kras/p53, and Kras/Lkb1 tumors

The researchers assessed activation of relevant intracellular pathways in tumors in treated and untreated mice with mutant Kras, Kras/p53, and Kras/Lkb1 lung cancers. They performed these studies using two different methods–immunostaining of cancer nodules for phosphorylated ERK, and immunoblotting of tumor lysates. In untreated mice, Kras/Lkb1 tumors show less activation of ERK than do Kras and Kras/p53 tumors, with Kras/p53 tumors showing the greatest amount of activation of the MEK-ERK pathway. Docetaxel had no discernible effect on signaling via the MEK-ERK pathway. Selumetinib alone resulted in decreased ERK activation in Kras and Kras/p53 tumors, but there was still residual activity. The docetaxel/selumetinib combination, however, was more effective in eliminating ERK activation. Pharmacokinetic studies indicated that selumetinib levels were higher in both serum and tumors of mice treated with docetaxel/selumetinib that in those treated with selumetinib alone; this might account for the more potent suppression of MEK-ERK signaling by the combination therapy as compared to selumetinib monotherapy. The researchers studied MEK-ERK activation (as determined by phospho-ERK staining) in  a set of 57 human NSCLC tumors with known RAS, p53 and LKB1 mutation status. As with the tumors in the mouse model, of seven patients whose tumors harbored the KRAS activating mutation, the three patients with concurrent p53 mutations showed higher levels of ERK activation.

The decreased activation of ERK in Kras/Lkb1 tumors suggested that these tumors utilize other pathways to drive their proliferation. On the basis of their prior studies of signal transduction in mutant-Lkb1 lung tumors, the researchers focused on AKT and SRC. Immunoblotting studies showed that Kras/Lkb1 mutant tumors had elevated activation of both AKT and SRC. As one can see from the figure at the top of this article, AKT is a downstream effector of PI3K; since the PI3K/AKT pathway regulates expression of GLUT1 and hexokinase, increased activation of the PI3K/AKT pathway is consistent with the increased uptake of FDG of mutant Kras/Lkb1 tumors. In the figure, SRC (which is not shown) represents one of the major “other effectors” controlled by RAS. These results indicate that concomitant mutation of Lkb1 in mutant-Kras NSCLCs may shift the signaling pathways that drive tumor proliferation from MEK-ERK to PI3K/AKT and/or SRC. This shift would result in primarily resistance of Kras/Lkb1 tumors to treatment with docetaxel/selumetinib.

Long-term benefits of treatment of mice with mutant-Kras and Kras/p53 tumors with docetaxel/selumetinib as opposed to docetaxel monotherapy

The researchers studied long-term treatment of mice with mutant-Kras and Kras/p53 tumors with docetaxel monotherapy versus docetaxel/selumetinib. In mice with mutant-Kras tumors, treatment with docetaxel monotherapy gave stable disease for several weeks, while docetaxel/selumetinib treatment resulted in tumor regression and slower regrowth of tumors. The addition of selumetinib to docetaxel significantly prolonged progression-free survival in these mice. In mice with Kras/p53 tumors, treatment with docetaxel alone resulted in progressive disease, but docetaxel/selumetinib treatment resulted in initial disease regression followed by progression, resulting in prolonged progression-free survival. These results indicate that treatment with combination therapy as opposed to docetaxel alone results in improved progression-free survival, but not cure, in mice with Kras– and Kras/p53-mutant tumors.

The researchers also investigated mechanisms of acquired tumor resistance in mice with mutant-Kras and Kras/p53 tumors, which had been treated long-term with docetaxel/selumetinib. In moribund animals that had received this treatment, all tumor nodules examined showed a recurrence of ERK phosphorylation. This suggested that acquired resistance could be at least in part due to reactivation of MEK–ERK signaling despite ongoing treatment with selumetinib. Evaluation of resistant tumor nodules suggested that more than one mechanism for pathway reactivation was occurring; study of these mechanisms is ongoing.

Conclusions of the new co-clinical study

The results of this co-clinical study predict that docetaxel/selumetinib combination therapy will be more effective than docetaxel monotherapy in several sub-classes of mutant-KRAS NSCLC. This prediction is consistent with the early results of a Phase 2 clinical trial of these two drug combinations in second-line treatment of patients with KRAS-mutant NSCLC.

However, the co-clinical trial also predicts that concurrent mutation of LKB1 in mutant-KRAS  tumors will result in primary resistance to docetaxel/selumetinib combination therapy, perhaps via activation of parallel signaling pathways such as AKT and SRC. Since LKB1 status is not being prospectively assessed in the ongoing human clinical trial, the presence of patients with cancers having concurrent LKB1 mutations may diminish the differences between treatment arms based solely on KRAS status. The results of the co-clinical trial suggests that researchers perform retrospective analysis of p53 and LKB1 status in samples from the concurrent human clinical trial. Future clinical trials should then be designed that involve prospective analysis to ensure sufficient enrollment of patients with all three genotypes to enable sufficiently powered sub-group analyses.

Although the results of the co-clinical trial indicate that patients with mutant KRAS/LBK1 tumors be excluded from trials of docetaxel/selumetinib treatment, the research group that has been conducting the co-clinical trial has also been conducting studies that may lead to treatment strategies for KRAS/LBK1 tumors.

The co-clinical trial also allowed researchers to design and validate biomarker strategies, specifically the potential use of the less-invasive FDG-PET to predict efficacy and to monitor treatment. The co-clinical animal-model study also enabled the discovery of mechanisms of both primary and acquired resistance that might benefit future clinical trials and discovery/development of drugs. (The studies on acquired resistance are in a early stage and are ongoing). Any mechanisms of acquired resistance discovered in co-clinical studies should be confirmed in human clinical trials by examining biopsy samples from patients who relapse on therapy. The ability to assess mechanisms of resistance in preclinical or co-clinical animal studies may enable researchers to design rational drug combination strategies that can be implemented in future clinical studies.

The results of the new co-clinical trial strengthens the contention that co-clinical trials in genetically-engineered mice can provide data that can predict the outcome of parallel human clinical trials. Co-clinical trials can also be used to generate new hypotheses for use in analyzing concurrent human trials, and for design of future clinical studies. Moreover, co-clinical trials can result in the validation of improved animal models for human cancers, which can be used in research and preclinical testing of oncology agents, and in validation of biomarkers for clinical studies in oncology. Given the inadequacy of “standard” xenograft models, which is a major factor in the high attrition rate of pipeline oncology drugs, the availability of validated genetically-engineered animal models may be expected to enable improved oncology drug development.

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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 November 3, 2011, Cambridge MA biotech firm Verastem announced that it was filing a prospectus for an initial public offering (IPO). At that time, the company was 15 months old.

Verastem is led by Christoph Westphal, MD, PhD, a founder and the former CEO of Sirtris and a veteran entrepreneur and venture capitalist. The IPO has been underwritten by UBS, Leerink Swann, Lazard Capital Markets, Oppenheimer & Co., and Rodman & Renshaw.

On January 27, 2012, Fierce Biotech reported that Verastem had announced the previous night that its IPO raised $55 million from the sale of 5.5 million shares at $10 apiece. This price fell exactly in the middle of its expected $9 to $11 price range, and the company had even increased the offering by a million shares over what had originally been planned.

On the same day, Verastem’s stock opened at $11 a share on the NASDAQ, up from its initial public offering price of $10.

Verastem not only has Christoph Westphal as its Chairman and CEO, but is also based on science from eminent MIT researchers Robert Weinberg, Ph.D. and Eric Lander, Ph.D., and has several other well-respected academic researchers (including Nobelist Phillip Sharp, Ph.D.) plus biotech industry drug discoverers Julian Adams, Ph.D. (MIllennium’s Velcade) and Roger Tung, Ph.D. (Vertex’ Lexiva and Agenerase) on its Scientific Advisory Board. The company has had considerable fundraising success prior to its IPO, including raising $32 million in venture capital  in July 2011.

However, Verastem has not one lone drug in human clinical trials, its most advanced compounds are in the preclinical stage, and the company does not plan to file an IND until 2013! Thus Verastem has successfully gone public, in an era in which even most private biotech companies with drugs in late-stage clinical trials are finding it very difficult to do so, despite its lack of any clinical-stage drugs.

As noted in the Fierce Biotech article, Dr. Westphal as well as other venture capital funders of Verastem agreed to buy up to $16.3 million of the IPO. This in part explains the success of the IPO. As also noted by Fierce Biotech, with over 19 million common shares outstanding, the offering valued Verastem at $192 million.

We discussed Verastem in our August 2, 2011 Biopharmonsortium Blog article entitled “Development of personalized therapies for deadly women’s cancers”. Verastem focuses on discovery and development of drugs to target cancer stem cells. Its technology is based on a strategy for screening for compounds that specifically target cancer stem cells, developed by Drs. Weinberg, Lander, Piyush Gupta (MIT and Broad Institute) and their colleagues.

Cancer stem cells are best known in acute myeloid leukemia (AML), but their existence in other cancers (especially solid tumors) is controversial, as discussed in our article. Whether cancer stem cells are involved in the pathobiology of solid tumors (or a particular type of solid tumor) or not, the biology of the putative cancer stem cell phenotype can be important in certain subtypes of cancer. Cancer stem cells are characterized by the epithelial-mesenchymal transition (EMT). In the Cell paper, the researchers screened for compounds that specifically targeted breast cancer cells that had been experimentally induced into an EMT, and which as a result exhibited an increased resistance to standard chemotherapy drugs.   They identified the compound salinomycin (now being marketed as a generic veterinary antibiotic) as a drug that specifically targeted these cells, as well as putative cancer stem cells from patients.

As we discussed in our article, triple-negative (TN) breast cancer cannot be treated with standard receptor-targeting breast cancer therapeutics (e.g., tamoxifen, aromatase inhibitors, trastuzumab) but must be treated with cytotoxic chemotherapy. It is generally more aggressive than other types of breast cancer, and even treatment with aggressive chemotherapy typically results in early relapse and metastasis. However, TN breast cancer includes two experimentally defined subtypes that have gene expression signatures related to the EMT. One or both of these subtypes might therefore be expected to be sensitive to compounds that specifically target putative breast cancer stem cells. This may be true whether the cancer stem cell hypothesis applies to TN breast cancer or not. Verastem is focusing on TN breast cancer as its first therapeutic target.

Verastem’s VS-507, a proprietary formulation of salinomycin, is being developed to treat TN breast cancer. The company is also screening for additional compounds, including New Chemical Entities (NCE) that can achieve stronger intellectual property protection than a salinomycin formulation. Verastem had not chosen a lead compound as of the middle of 2011. The company is now reported to be doing preclinical studies on three of its compounds, and also plans to create diagnostic tests to identify patients that could benefit from its treatments. (As we discussed in our article, biomarker-based tests will be critical in making such therapies work.)

As one can discern from our blog article, we are intrigued by Verastem’s approach to cancer treatment, and especially its approach to TN breast cancer. The science behind Verastem’s drug discovery strategy, developed by 2011 ASCO award-winning oncogene and cancer stem-cell pioneer Bob Weinberg, is very compelling. We would love to see Verastem’s therapeutic strategy succeed.

However, as virtually all pharmaceutical and biotechnology R&D researchers well know, it is difficult to translate even the most compelling science developed by the most brilliant researchers into the clinic. Even therapeutic strategies with an excellent scientific rationale that have achieved proof of principle in the best animal models can result in clinical failure, especially with the first compound tested in proof-of-concept studies in human patients. The cancer stem cell hypothesis remains controversial. Moreover, diseases such as TN breast cancer are complicated, they may have mechanisms of resistance to a new experiential therapy that no one knows about, and our understanding of disease biology is limited.

Thus at least until Verastem’s therapies achieve proof of concept in human studies, purchase of Verastem stock is risky indeed. Moreover, there are other risks involved other than technical and clinical risk–especially competition for developing cancer stem cell-based therapies by other biotech/pharma companies. Venture capitalists (and certain knowledgeable individual investors and funds) are in the business of taking on high-risk investments for the sake of potential large rewards, but ordinary retail investors in the public markets are not. Therefore, it seems too early for Verastem to go public, even if it has founders and investors with enough clout to make an IPO successful.

Expert analysts in the IPO field, as stated in the Fierce Biotech article, are puzzled by the rationale for Verastem going public at this time. The financial news and services website “TheStreet.com” agrees. Our own sense of puzzlement is symbolized by the interobang (‽) in the title of this article.

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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.