Two recent research reports may point the way to developing more effective, personalized therapies for two deadly women’s cancers for which their are currently few treatment options–triple-negative breast cancer and ovarian cancer. The approach followed in both reports is to use gene expression analysis to stratify each of the two diseases into subtypes. Researchers can then use gene expression and order aspects of the biology of each subtype to design subtype-specific targeted therapies, whether single drugs or drug combinations. If the drugs (whether approved or experimental) already exist, they can be tested in clinical trials, stratified by subtype. If no appropriate drugs exist, researchers can discover the drugs based on subtype-appropriate drug targets.

Triple-negative (TN) breast cancer refers to breast cancers that are negative for expression of estrogen receptor (ER), progesterone receptor (PR), and HER2. [HER2 is the target of trastuzumab (Roche/Genentech’s Herceptin) and lapatinib (GlaxoSmithKline’s Tykerb/Tyverb)]. Lacking all three receptors, it cannot be treated with standard receptor-targeting breast cancer therapeutics (e.g., tamoxifen, aromatase inhibitors, trastuzumab) but must be treated with cytotoxic chemotherapy. TN breast cancer is generally more aggressive than other types of breast cancer, and even treatment with aggressive chemotherapy regimens typically results in early relapse and metastasis.

TN breast cancers constitute approximately 25 percent of breast cancers. They are diagnosed most often in younger women, those who have recently given birth, women with BRCA1 mutations, and African-American and Hispanic women.

There is a Triple Negative Breast Cancer Foundation, which was founded in 2006 in honor of a mother in her mid-thirties who died of the disease.

Ovarian cancer, the ninth most common cancer in women, caused nearly 14,000 deaths in the U.S. in 2010. In its earliest stages, its symptoms are usually very subtle and mimic other, less serious diseases. As a result, it is usually detected at later stages in which treatment is more difficult and gives poorer outcomes. The 2001 five-year survival rate was 47%, up from 38% in the mid-1970s. This compared to an overall survival rate for cancer of 68% in 2001, up from 50% in the mid-1970s.

Treatment usually involves surgery and chemotherapy, and sometimes radiotherapy. Surgery (preferably by a gynecological oncologist) may be sufficient for earlier-stage tumors that are well-differentiated and confined to the ovary. In this early-stage disease (which represents about 19% of women presenting with ovarian cancer), the five-year survival rate is 92.7%. However, about 75% of women presenting with ovarian cancer already have stage III or stage IV disease, in which the cancer has spread beyond the ovaries. Then the prognosis is much poorer, and the vast majority of patients will have a recurrence.

The triple-negative breast cancer study

The TN breast cancer study was carried out by researchers at the Vanderbilt-Ingram Cancer Center (Vanderbilt University, Nashville, TN), and published in the 1 July 2011 issue of the Journal of Clinical Investigation. In this study, the researchers analyzed gene expression profiles from 21 publicly available breast cancer data sets, and identified  587 cases of TN breast cancer (by non-expression of mRNAs that encode ER, PR, and HER2). Using cluster analysis, they identified six TN breast cancer subtypes:

• two basal-like subtypes (BL1 and BL2),
• an immunomodulatory (IM) subtype (i.e., expressing genes involved in immune cell processes)
• a mesenchymal (M) subtype
• a mesenchymal stem–like (MSL) subtype
• a luminal androgen receptor (LAR) subtype.

Using gene expression analysis, the researchers identified TN breast cancer model cell lines that were representative of each of these subtypes. On the basis of their analysis, the researchers predicted “driver” signaling pathways, and targeted them pharmacologically as a proof-of-principle that analysis of gene expression signatures of cancer subtypes can inform selection of therapies.

BL1 and BL2 subtypes had higher expression of genes involved in the cell cycle and response to DNA damage, and model cell lines preferentially responded to cisplatin. M and MSL subtypes were enriched for expression of genes involved in the epithelial-mesenchymal transition (EMT), and growth factor-related pathways in model cell lines responded to the PI3K/mTOR inhibitor BEZ235 (Novartis, now in Phase 1 and 2 for solid tumors) and to the ABL/SRC inhibitor dasatinib [Bristol-Myers Squibb’s Sprycel, currently approved for treatment of chronic myelogenous leukemia (CML) and Philadelphia chromosome-positive acute lymphoblastic leukemia (ALL), and under investigation for treatment of solid tumors). The LAR subtype was characterized by androgen receptor (AR) signaling, and included patients with decreased progression-free survival. LAR model cell lines were uniquely sensitive to the AR antagonist bicalutamide (AstraZeneca’s Casodex/Cosudex, currently approved for the treatment of prostate cancer and hirsutism, and under investigation for treatment of androgen receptor-positive, ER negative, PR negative breast cancer).

The researchers plan to use the TN breast cancer subtype-specific model cell lines for further molecular characterization, to identify new components of the “driver” signaling pathways for each subtype. These pathways can be targeted in further drug discovery efforts. The subtype-specific cell lines can also be used in preclinical studies with targeted agents, and in identification of subtype-specific biomarkers that can potentially be used in stratifying TN breast cancer patients so that they might be treated with the best agents for their disease.

The ovarian cancer study

The ovarian cancer study was carried out by the Cancer Genome Atlas Research Network [a consortium of academic researchers jointly funded and managed by the National Cancer Institute (NCI) and the National Human Genome Research Institute (NHGRI)], and published in the 30 June 2011 issue of Nature. In this study, the researchers analyzed mRNA expression, microRNA expression, promoter methylation and DNA copy number in 489 high-grade serous ovarian adenocarcinomas, as well as the DNA sequences of exons from coding genes in 316 of these tumors. Serous adenocarcinoma is the most prevalent form of ovarian cancer, accounting for about 85 percent of all ovarian cancer deaths.

The researchers found that nearly all of the high-grade serous ovarian cancers (HGS-OvCa) studied had mutations in the TP53 gene, which encodes the p53 tumor suppressor protein. On the basis of their gene expression (mRNA) signatures, the researchers divided the population of HGS-OvCa into four subtypes:

• an immunoreactive subtype (i.e., expressing genes involved in immune cell processes)
• a differentiated subtype (high expression of markers of differentiated female reproductive tract epithelia)
• a proliferative subtype (high expression of markers of cell proliferation)
• a mesenchymal subtype (high expression of HOX genes and of markers of mesenchymal-derived cells)

The researchers also determined subtypes on the basis of microRNA expression and promoter methylation. microRNA subtype 1 overlapped the mRNA proliferative subtype and miRNA subtype 2 overlapped the mRNA mesenchymal subtype. Patients with miRNA subtype 1 tumors survived significantly longer that those with tumors of other microRNA subtypes.

Although the researchers found no significant difference in survival between the four transcriptional subtypes, they did identify a 193-gene expression signature that was predictive of overall survival. 108 genes were correlated with poor survival and 85 were correlated with good survival.

The researchers identified cancer-associated pathways in the HGS-OvCA population; this is equivalent to the prediction of “driver” signaling pathways in the TN breast cancer study. They found that 20% of the HGS-OvCA samples had germline or somatic mutations in BRCA1 or BRCA2, and that 11% lost BRCA1 expression through DNA hypermethylation. As we discussed in an earlier article on this blog, BRCA1- or BRCA2-negative tumor cells cannot repair their DNA via homologous recombination. They are dependent on an alternative pathway of DNA repair, which involves the enzyme poly(ADP) ribose polymerase (PARP). These tumors are thus sensitive to a class of drugs known as PARP inhibitors, such as KuDOS/AstraZenaca’s olaparib. There are now six PARP inhibitors, including olaparib, in clinical development.

The researchers found genetic alterations in several other genes involved in homologous recombination. Altogether, defects in homologous recombination may be present in approximately half of HGS-OvCa cases, and these tumors may be sensitive to PARP inhibitors. This provides a rationale for clinical trials of PARP inhibitors in women with ovarian cancers with defects in homologous recombination-related genes.

Olaparib and other PARP inhibitors are in clinical trials in women with advanced with BRCA-1 or -2 mutations and with other defects in homologous recombination. As discussed in the 2011 ASCO meeting, early Phase 2 results indicate that olaparib gives dramatic improvements in progression-free survival in these women. (See this article.) In these studies, in addition to tumors with genetic defects in homologous recombination, olaparib or another PARP inhibitor, Abbott’s ABT-888, appears to give improved progression-free survival in women who have previously been treated with chemotherapy drugs that result in DNA damage. This suggests that oncologists may be able to use a “one-two punch”, consisting of a DNA-damaging drug [such as the alkylating agent temozolomide [Merck’s Temodar]) followed by a PARP inhibitor, to treat advanced ovarian cancer.

In addition to BRCA-1 and BRCA-2 mutations and other genetic alterations that result in defects in homologous recombination, the HGS-OvCa population exhibited genetic changes that would result in deregulation of several other cancer related pathways. These pathways included the RB1 (67% of cases), RAS/PI3K (45% of cases), and NOTCH (22% of cases) pathways, as well as the FOXM1 transcription factor network (87% of cases). All of these pathways represent opportunities for target identification and drug discovery. FOXM1 (Forkhead box protein M1) was named the Molecule of the Year for 2010 by the International Society for Molecular and Cell Biology and Biotechnology Protocols and Research (ISMCBBPR) because of “its growing potential as a target for cancer therapies.” FOXM1 overexpression results in destabilization of the cell cycle, which can lead to a malignant phenotype.

The researchers also identified 22 genes that were frequently amplified or overexpressed in HGS-OvCA tumors (other than genes that are involved in homologous recombination). Inhibitors (including approved and experimental compounds) already exist for the products of these genes, and researchers might assess these compounds in HGS-OvCa cases in which target genes are amplified.

Can Verastem develop new therapeutics for triple negative breast cancer?

The private biotechnology company Verastem (Cambridge, MA) focuses on discovery and development of drugs to target cancer stem cells. The company was founded in 2010, and is based on a strategy for screening for compounds that specifically target cancer stem cells. This strategy, published in the journal Cell in 2009, was developed by Drs. Robert Weinberg (MIT Whtehead Institute), Eric Lander (Broad Institute of MIT and Harvard University), and Piyush Gupta (MIT and Broad Institute) and their colleagues. Drs. Weinberg, Lander, and Gupta are on the Scientific Advisory Board of Verastem.

On July 14, 2011, Verstem announced that it had raised $32 million in a Series B financing. Verastem had previously raised $16 million from a group led by former Christoph Westphal’s Longwood Founders Fund. Dr. Westphal (formerly of Sirtris) is now Chairman of Verastem.

Cancer stem cells are best known in acute myeloid leukemia (AML), but their existence in other cancers (especially solid tumors) is controversial. The cancer stem cell hypothesis asserts that a small subpopulations of cells in a leukemia or solid tumor have characteristics that resemble normal adult stem cells, such as self renewal, the ability to give rise to all the cell types found in the leukemia or cancer, and stem cell markers. The hypothesis further asserts that most cancer treatments fail to knock out cancer stem cells, which can repopulate a tumor cell population, resulting in treatment relapses. Cancer stem cell researchers therefore propose developing cancer stem-cell specific therapeutics that can be used to eliminate these cells, which can block these relapses.

Whether cancer stem cells are involved in the pathobiology of solid tumors 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), and 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 as a drug that specifically targeted these cells, as well as putative cancer stem cells from patients.

As discussed earlier in this article, TN breast cancer includes two subtypes that have gene expression signatures related to the EMT: the mesenchymal (M) subtype and the mesenchymal stem–like (MSL) subtype. One or both of these subtypes might 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 recognizes this, and is thus focusing on TN breast cancer as its first therapeutic target. The Vanderbilt TN breast cancer study suggests that trials of any “cancer stem cell-specific” therapeutics for TN breast cancer should be guided by subtype-specific biomarkers.

Hope for treatment of TN breast cancer and advanced ovarian cancer

Researchers and oncologists have made great strides in increasing the percentage of breast cancers that are treatable or even curable in recent years. For example, prior to the FDA approval of trastuzumab in 1998, HER2 positive breast cancer carried a grim prognosis. But the advent of trastuzumab (and later, lapatinib) has had a major impact on treatment of this once uniformly deadly type of breast cancer.

We hope that the new, personalized medicine-based approach to TN breast cancer and advanced serous ovarian adenocarcinoma will also result in successful new therapeutic strategies for these deadly women’s cancers.

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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 time for the July 2011 World Drug Targets Summit in Cambridge MA is looming closer and closer! Registration for the conference is still open, however.

I will lead a workshop entitled “Developing Improved Animal Models in Oncology and CNS Diseases to Increase Drug Discovery and Development Capabilities” at the Summit on July 19.  A workshop on addressing kinase signaling in drug discovery and development will take place later that day. The main conference follows on July 20-21. I am planning to attend the entire conference.

Our workshop will be a discussion of four case studies involving development of novel animal models in oncology and CNS diseases, aimed at more closely modeling human disease than current models. Drug discovery and development in these therapeutic areas has been severely hampered by animal models that are  poorly predictive of efficacy. This is a major cause of clinical attrition in these areas.

There will be one case study on a zebrafish cancer model, two on mouse cancer models, and one on a mouse CNS disease model. The case studies will include applications of these animal models to understanding disease biology, developing new therapeutic strategies, overcoming resistance to breakthrough targeted cancer therapeutics, and identifying drug candidates and advancing them into the clinic.

The main conference will focus on developing improved target discovery and validation strategies that are capable of meeting the challenges of drug discovery and development in the early 21st century–minimizing drug attrition in the clinic, and delivering commercially differentiated products that address unmet medical needs to the market. Speakers will include target discovery and validation leaders from leading pharmaceutical companies, biotechnology companies, and academic institutions.

On June 1, 2011, Cambridge Healthtech Institute’s (CHI’s) Insight Pharma Reports announced the publication of our new book-length report, Multitargeted Therapies: Promiscuous Drugs and Combination Therapies.

In the past 20 years or so, pharmaceutical and biotechnology industry R&D has been increasingly aimed at developing drugs to treat complex diseases such as cancer, cardiovascular disease, type 2 diabetes, and Alzheimer’s disease. However, the one drug-one target-one disease paradigm that has become dominant in the post-genomic era has proven to be inadequate to address complex diseases, which have multiple “causes”, and each of which may be more than one disease. This has been a major cause of clinical failure and the low productivity of the pharmaceutical industry.

Moreover, researchers have found that most of the successful, FDA-approved small-molecule drugs that were developed prior to the year 2000 are promiscuous, i.e., they are single drugs that address multiple targets. In addition, the great majority of kinase inhibitors, one of the most successful drug classes of the early 21st century, are also promiscuous.

The study of small-molecule drug promiscuity has spawned the emerging field of network pharmacology, which can be applied both to study drug promiscuity and to rationally design small-molecule multitargeted drugs. (Researchers can discover or design multitargeted kinase inhibitors without the use of network pharmacology, however.)

Meanwhile, the development of targeted drugs such as kinase inhibitors and monoclonal antibodies has resulted in the need to develop multitargeted combination therapies. This has been especially true in cancer, where disease causation may involve multiple signaling pathways. In particular, the development of resistance to targeted antitumor drugs has spawned the need to develop second-generation treatments, many of which are multitargeted combination therapies.

Our report covers both discovery and design of small-molecule promiscuous/multitargeted drugs, and of multitargeted combination therapies.

The design of multitargeted combination therapies is one of the hottest areas of cancer R&D today, especially with respect to developing means to overcome resistance to targeted therapies. This area was the focus of many key presentations at the 2011 American Society of Clinical Oncology (ASCO) Annual Meeting, which was held in Chicago on June 3-7. For example, treatment with vemurafenib (PLX4032) of metastatic melanoma patients whose tumors carry the B-Raf(V600E) mutation has produced spectacular overall response rates and increased survival. However, in nearly all cases, the tumors relapse. The latest results with vemurafenib were discussed at ASCO 2011, as well as strategies to overcome resistance to therapy. Our new report also discusses strategies for overcoming vemurafenib resistance, all of which involve design of multitargeted combination therapies.

Another topic discussed at ASCO 2011 was antitumor strategies based on synthetic lethality. We discussed this strategy in an earlier article on this blog, especially with respect to poly(ADP) ribose polymerase (PARP) inhibitors such as KuDOS/AstraZenaca’s olaparib. At a session at the ASCO meeting entitled “PARP Inhibitors, DNA Repair, and Beyond: Theory Meets Reality in the Clinic”, speakers reviewed current progress in developing PARP inhibitors, of which six are now in clinical development.

This session also included a presentation by Michael B. Kastan, MD, PhD (St. Jude Children’s Research Hospital, Memphis TN) on other ways of using the synthetic lethally strategy, for example by targeting kinases involved in DNA repair pathways such as ATM (Ataxia-Telangiectasia Mutated) or Chk1 checkpoint kinase, or even utilizing features of the tumor microenviroment such as hypoxia. Such strategies might be used to design multitargeted combination therapies that specifically target cancer cells with defects in DNA repair and/or in hypoxic solid tumors, and/or to sensitize cancer cells to radiation.

Our new report includes a chapter on using the synthetic lethality strategy to design combination therapies of a cytotoxic drug with a chemosensitizing agent, and to develop therapies for p53-negative cancers. (The key tumor suppressor p53 is deleted, mutated, or inactivated in the majority of human cancers).

Although design of multitargeted combination therapies, as well as discovery and design of kinase inhibitors, are of key importance for current oncology R&D and are also being applied to other diseases, design of single small-molecule multitargeted drugs via network pharmacology is an early-stage, and perhaps a premature, technology. Nevertheless, given the current pharmaceutical company R&D business model that emphasizes outsourcing early-stage R&D, academic research groups and biotechnology companies that are active in this area may be able to forge partnerships with pharmaceutical companies.

For more information on Multitargeted Therapies: Promiscuous Drugs and Combination Therapies, or to order it, see the Insight Pharma Reports website.

Niacin (nicotinic acid)

In our blog post of May 19, 2011, we discussed the late-stage development of two cholesterol ester transfer protein (CETP) inhibitors, designed to raise serum high-density lipoprotein (HDL), or “good cholesterol”. These agents are Merck’s anacetrapib and Roche’s dalcetrapib. The clinical results with these agents have  have reignited enthusiasm for CETP inhibitors in the medical and drug discovery and development community.

Now comes the news that The National Heart Lung and Blood Institute (NHLBI) of the National Institutes of Health (NIH) stopped a large clinical trial of Abbott’s Niaspan, an extended-release formulation of high-dose niacin, because the drug failed to prevent heart attacks and strokes. High-dose niacin is the only drug that is approved for raising HDL. Generic high-dose niacin is usually taken 2-3 times per day, and can cause adverse effects such as skin flushing and itching. Niaspan, as an extended-release formulation of the drug, is taken once a day, and was developed to reduce the extent of these adverse effects. Niaspan is an FDA-approved drug.

Merck has meanwhile been developing its high-dose non-flushing niacin product, Tredaptive/Cordaptive (extended-release niacin/laropiprant). This is a combination product consisting of extended-release high dose niacin plus  laropiprant. Laropiprant is designed to block the ability of prostaglandin D2 to cause skin flushing; niacin-induced skin flushing works via the action of prostaglandin D2 in the skin. In 2008, the FDA rejected Merck’s New Drug Application for Tredaptive/Cordaptive, so the drug remains investigational in the US. However, in 2009 Merck launched Tredaptive in international markets including Mexico, the UK and Germany. The drug is approved in over 45 countries. Merck is also conducting a 25,000-person trial of Tredaptive for reducing the rate of cardiovascular events in patients who are at risk for cardiovascular disease (CVD). Merck intends to file for approval of the drug in the US in 2012, based on the results of this trial if it is positive.

According to an NIH press release, the NHLBI trial, known as AIM-HIGH, involved combination therapy with Niaspan and a statin (simvastatin). Participants selected for the trial had been taking a statin and had well-controlled LDL, but were still at risk for cardiovascular events since they had a history of CVD, as well as low serum HDL and high serum triglycerides. In the treatment arm of the study, participants received a combination of a stain and Niaspan, while those in the control arm received a statin plus placebo.

During the 32 months of the study, subjects in the treatment arm exhibited increased HDL and lower triglyceride levels, as compared to participants in the control arm.  However, combination Niaspan/statin treatment did not reduce cardiovascular events or strokes as compared to statin treatment plus placebo. The NIH therefore stopped the trial 18 months earlier than planned.

In the AIM-HIGH study, subjects had a lower rate of cardiovascular events and strokes than the trial researchers expected. Of the 1,718 people in the treatment arm, 5.8 people per year had cardiovascular events, as opposed to 5.6 cardiovascular events per year among the 1,696 people in the control arm. There was a small increased rate of strokes in patients taking Niaspan, but researchers cautioned that this may have been due to chance. However, the increased rate of strokes, along with the failure to demonstrate efficacy, contributed to the NHLBI’s decision to end the trial early.

As noted by the AIM-HIGH researchers (and mentioned in the NIH press release), the lack of efficacy of high-dose niacin was unexpected, and in striking contrast to the results of previous trials and of observational studies. For example, a 2010 meta-analysis of clinical trials evaluating niacin, alone or in combination with other lipid-lowering drugs (published between 1966 and mid-2008) found significantly positive effects of niacin in preventing cardiovascular events and in reversing or slowing the progression of atherosclerosis. However, the bulk of the studies analyzed had been performed before statin therapy had become the standard of care. As pointed out in a recent article by clinical outcomes researcher Harlan Krumholz, MD (Yale University School of Medicine), it was important to compare Niasapn with a good treatment–in this case, the standard treatment with a statin–rather than comparing it to a poor treatment or to placebo alone.

The results of the AIM-HIGH study may not apply to other patient populations, including higher-risk groups such as patients with acute heart attack or acute coronary syndromes, or in patients who have poorly-controlled LDL despite statin treatment. As a press release from Abbott pointed out, the relevance of the results of AIM-HIGH to patient populations other than the one studied–patients with stable, non-acute, pre-existing cardiovascular disease and very well controlled LDL on simvastatin–is unknown. However, it is not known whether there are any patient populations that might benefit from treatment with Niaspan plus a statin as compared to a statin alone.

The results of AIM-HIGH also do not apply to other drugs that are designed to raise levels of serum HDL. Each drug must be tested in the clinic before drawing conclusions about its efficacy and safety. Various drugs may have different effects on human disease biology. Thus, for example, one should not use the results of the AIM-HIGH trial of Niaspan to conclude that the CETP inhibitors anacetrapib and dalcetrapib, discussed in our previous blog post, are not likely to be efficacious.

The 19 May issue of Nature contains a special Insight section on cardiovascular biology. An article in this section, by leading cardiovascular researcher Peter Libby (Brigham and Women’s Hospital, Boston MA, where he is the Chief of the Division of Cardiovascular Medicine) and his colleagues, is entitled “Progress and challenges in translating the biology of atherosclerosis”. That article refers to HDL as a “frustrating next frontier” (beyond lowering LDL with statins) in cardiovascular drug treatment. HDL biology is complex, with HDL promoting efflux of cholesterol from macrophages in atherosclerotic plaques and exerting anti-inflammatory and other beneficial effects, as also discussed in our previous blog post. HDL particles in blood serum are heterogeneous, with some HDL particles having a greater degree of positive effects on atherosclerotic plaque biology than others. As a result, treatments (e.g., drugs, diet) that raise HDL, as determined by standard clinical assays for serum HDL, may not necessarily result in clinical benefit, because of qualitative changes in populations of HDL particles.

In this connection, the 2010 study by Alan Tall and his colleagues, which we discussed in our May 19, 2011 blog article, provides hope for the efficacy of anacetrapib. These researchers showed that although niacin treatment in humans resulted in a moderate increase in the ability of HDL to promote net cholesterol efflux (measured in in vitro assays), anacetrapib treatment caused a more dramatic increase. This was due not only to a higher level of HDL in anacetrapib-treated subjects, but also to enhanced ability of anacetrapib-induced HDL particles to promote cholesterol efflux, especially at high HDL concentrations. Although this study suggests that anacetrapib treatment induces increases in HDL particles that promote beneficial effects on atherosclerotic plaque biology, we must wait for the results of the REVEAL trial (expected in 2014-2016) to determine the efficacy of this drug. Meanwhile, the clinical trial of Roche’s CETP inhibitor dalcetrapib, known as dal-OUTCOMES, is ongoing, with efficacy results expected in 2012-2013.

Steven Nissen, M.D. (chief of cardiovascular medicine at Cleveland Clinic), a veteran HDL researcher who has often been critical of the pharmaceutical industry, was recently interviewed on public television about the AIM-HIGH trial. He said that ever since the introduction of statins in 1987, we have not had a successful new drug class that provides significant clinical benefits by modulating serum lipids. Even when new types of lipid-modulating drugs have given apparently better biochemical results (e.g., LDL lowering or HDL raising), they have not provided clinical benefit in terms of preventing cardiovascular events.

Nevertheless, despite past disappointments with HDL-raising therapies, and despite the results of AIM-HIGH, Dr. Nissen persists in running clinical studies of novel HDL-raising drugs. He is now working on testing Resverlogix’ (Calgary Alberta, Canada) RVX-208, a small-molecule drug related to resveratrol that induces endogenous production of the protein component of HDL, apolipoprotein A1. And, as discussed in our last blog post, Dr. Nissen is enthusiastic about the prospects of Merck’s anacetrapib, although he states that the FDA will require hard clinical evidence of this drug’s efficacy before approving it.

Statins, despite their leading role in cardiovascular therapy, only reduce the risk of heart attack and stroke by 25% to 35%. Thus there is the need for new classes of drugs, and HDL is–frustrating though it be–the next frontier. Thus researchers persist in discovery and development of HDL-raising drugs, and there are promising new candidates on the horizon.

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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.

Atherosclerosis. From Nephron. http://bit.ly/jL6Zos

In the April 29, 2011 issue of Cell, there is a Leading Edge review entitled “Macrophages in the Pathogenesis of Atherosclerosis”, by Kathryn J. Moore (New York University Medical Center, New York, NY ) and Ira Tabas (Columbia University, New York, NY). This 15-page  review (including 4 pages of references) covers a big subject–the central role of the macrophage in the pathogenesis of atherosclerosis, and of the resulting acute thrombotic vascular disease, including myocardial infarction, stroke, and sudden cardiac death. The review will be helpful to those who wish to update their knowledge of the mechanistic basis of atherothrombotic disease, or to those who want an introduction to the subject.

Included in the review is a discussion of the role of high-density lipoprotein (HDL), or “good cholesterol” in promoting regression of atherosclerotic plaques. HDL, as well as the protein component of HDL, apolipoprotein A1, are key players in the process of cholesterol efflux, or removal of cholesterol from macrophages in atherosclerotic plaques. HDL may also have other beneficial roles, including prevention of subendothelial apolipoprotein B-lipoprotein (apoB-LP) retention (which starts the atherosclerotic process in the first place), decreasing activation of endothelial cells, and reducing LDL oxidation. (ApoB is the protein component of low-density lipoprotein [LDL], or “bad cholesterol”.) In human populations, low HDL is generally recognized as a major cardiovascular risk factor, and high HDL is recognized as being protective.

In its discussion of therapeutic strategies based on our current picture of the mechanistic basis of atherosclerosis, the authors of the review state that the most effective way to treat the condition would be to decrease subendothelial apoB-LP retention by lowering apoB-LPs in the blood via lifestyle changes and drugs. In order to completely prevent atherosclerosis, serum apoB-LPs (i.e., mainly LDL and VLDL [very low-density lipoprotein]) would need to be lowered below the threshold level required for subendothelial apoB-LP retention in the arteries. However, in Western societies (and in other societies that have been rapidly adopting Western lifestyles), initiation of atherosclerotic lesions occurs in the early teens; thus this preventive approach is not currently feasible.

The leading drugs for lowering serum LDL are the statins, such as atorvastatin (Pfizer’s LIpitor, which is the largest-selling statin; Lipitor will go off-patent in November 2011), pravastatin (Bristol-Myers Squibb’s Pravachol, generics), simvastatin (Merck’s Zocor, generics), and rosuvastatin (AstraZeneca’s Crestor). Statins are generally accepted as being effective in decreasing mortality in patients with cardiovascular disease (CVD). These drugs are also widely prescribed for patients with a high risk of developing CVD; i.e., patients with high LDL, type 2 diabetes, and/or other risk factors. However, some researchers question the value of statins in primary prevention in patients without preexisting CVD but at high risk of developing the disease. For example, a 2010 meta-analysis published in the Archives of Internal Medicine did not find evidence that statin therapy was beneficial in primary prevention of all-cause mortality in patients at high risk of developing CVD. Moreover, although statins are highly effective in decreasing cardiovascular events (up to 60%) and cardiovascular deaths in patients with pre-existing CVD, a large percentage of patients with or at high risk of developing CVD, despite statin treatment, still experience cardiovascular events and cardiovascular death. Therefore, researchers and companies would like to develop other, complementary drugs that work via different mechanisms from the statins.

HDL raising has long been a key target for pharmaceutical and biotechnology companies in their quest to develop CVD drugs that would be complementary to the statins. In the early-to-mid 2000’s, companies had several candidate drugs, of different types, in development. In an article published by Pharmaceutical Executive in 2006, I was quoted as saying that raising HDL was a big field. However, most of the drugs being developed at that time fell by the wayside, mainly due to failure in the clinic.

A particular focus of pharmaceutical companies has been the development of cholesteryl ester transfer protein (CETP) inhibitors. CETP catalyzes the transfer of cholesteryl esters and triglycerides between LDL/VLDL and HDL, and vice versa. In vivo (in animals and in humans), CETP inhibitor drugs raise HDL and lower LDL.

The leading CETP inhibitor in the early to mid-2000s was Pfizer’s torcetrapib. Pfizer had placed high hopes on torcetrapib, as a potential blockbuster to replace anticipated lost revenues from Lipitor when it went off-patent in 2011. However, in late 2006 Pfizer pulled the drug from Phase 3 trials, after finding that combination therapy with torcetrapib  and atorvastatin gave a 50 percent greater mortality rate that atrovastatin alone. This was not only a huge disappointment for Pfizer and its shareholders, but also cast a pall of gloom over the entire HDL-raising drug field, and especially over CETP inhibitors. Researchers speculated that inhibition of CETP might result in producing a form of HDL that is not cardioprotective, and might even be harmful. There were even calls for pushing the HDL field back to the basic research level, with the need to find just how (and what form of) HDL exerted its cardioprotective effects, in people with elevated HDL due to genetics, lifestyle, or treatment with high-dose niacin (the only drug approved to raise HDL).

However, later studies of torceptrapib found that the toxicity of the compound was not due to an untoward effect of CETP inhibition or HDL raising, but was due to off-target effects of the drug. In animals and in humans, torceptrapib raised serum levels of aldosterone, via release of aldosterone from the adrenals. Aldosterone was responsible for the increase of blood pressure seen in animals and in humans treated with torceptrapib, and aldosterone has proatherogenic effects that go beyond its effects on blood pressure. The hypertensive and aldosterone-raising effects of torceptrapib were independent of its CETP inhibitor activity, and other CETP inhibitors (discussed below) do not raise aldosterone levels or blood pressure.

A March 2011 News and Analysis article in Nature Reviews Drug Discovery reviewed the history of the CETP inhibitor field after the demise of torcetrapib. Although the torcetrapib debacle caused several other companies to exit the CETP inhibitor field, Roche and Merck persisted. Roche has been developing the CETP inhibitor  dalcetrapib, and Merck’s CETP inhibitor is known as anacetrapib.

As mentioned in the Nature Reviews Drug Discovery mini-review, Dr. Alan Tall (Columbia University), working in collaboration with Merck researchers, showed in 2010 that niacin treatment in humans resulted in a 30% increase in HDL, while anacetrapib treatment resulted in a 100% increase in HDL. Niacin treatment in humans resulted in a moderate increase in the ability of HDL to promote net cholesterol efflux (measured in in vitro assays) while anacetrapib treatment caused a more dramatic increase. This was due not only to a higher level of HDL in anacetrapib-treated subjects, but also to enhanced ability of anacetrapib-induced HDL particles to promote cholesterol efflux, especially at high HDL concentrations. HDL from both niacin-treated and anacetrapib-treated subjects also exhibited anti-inflammatory activity. This study should help lay to rest the idea that pharmacological inhibition of CETP might result in abnormal pro-atherogenic HDL, as theorized by some researchers after the clinical failure of torceptrapib.

Currently, Roche’s dalcetrapib is in a 15,600-patient Phase 3 clinical trial known as dal-OUTCOMES; this trial was initiated in 2008, and efficacy results are expected in 2012-2013. As of the time of the Nature Reviews Drug Discovery article, Merck planned to initiate its 30,000-patient REVEAL trial of anacetrapib in April 2011. Efficacy results of REVEAL are anticipated in 2014-2016.

In December 2010, the results of Merck’s moderate-sized (1623 patients with or at high risk for CVD, who were already being treated with a statin) Phase 3 DEFINE trial of anacetrapib were published in the New England Journal of Medicine. The DEFINE trial was designed as a safety study. In this 76-week study, anacetrapib showed no significant differences from placebo in terms of safety, as measured by a pre-specified cardiovascular endpoint (defined as cardiovascular death, myocardial infarction, unstable angina or stroke). These cardiovascular events occurred in 16 anacetrapib-treated patients (2.0 percent) compared with 21 placebo-treated patients (2.6 percent). There were also no significant differences in blood pressure, serum electrolytes, or aldosterone levels between anacetrapib-treated and placebo-treated patients.

Anacetrapib treatment also decreased LDL by 40 percent (from 81 to 45 mg/dl vs. 82 to 77 mg/dl for placebo) and increased HDL by 138 percent (from 40 to 101 mg/dl vs. 40 to 46 mg/dl for placebo). Anacetrapib also had other favorable effects on lipid levels (e.g., 36.4% reduction in lipoprotein(a), and 6.8% reduction in triglycerides, beyond the changes seen with placebo treatment).

Although the DEFINE study was too small to provide definitive results regarding the safety of anacetrapib, it gave a 94% predictive probability that treatment with anacetrapib is not associated with the rate of cardiovascular events seen with torcetrapib. The trial also indicated that anacetrapib treatment does not result in the effects (especially raising of serum aldosterone levels) thought to be responsible for torcetrapib’s toxicity. Moreover, anacetrapib treatment resulted in a dramatic increase in HDL levels (beyond that seen with torcetrapib) in the DEFINE study, and the 2010 study by Dr. Tall and his colleagues indicates that anacetrapib-induced HDL is highly effective in promoting cholesterol efflux.

The results with anacetrapib have reignited enthusiasm for CETP inhibitors in the medical community. Even the often-critical Dr. Steven Nissen (Cleveland Clinic) expressed enthusiasm for anacetrapib. However, despite these promising results, the efficacy of CETP inhibitors, in terms of significantly reducing the rate of cardiovascular events, has not yet been demonstrated. Only large, adequately-powered Phase 3 clinical trials, such as dal-OUTCOMES for Roche’s dalcetrapib and REVEAL for Merck’s anacetrapib, can definitively establish both the efficacy and the safety of these drugs.

The development of CETP inhibitors represents a situation in which the leading drug in the class failed because of off-target effects. However, these off-target effects were not class effects, and targeting CETP in order to raise HDL now seems like a good idea after all. Pfizer ignored warning signs (especially the modest elevation in blood pressure induced by torcetrapib, which did not appear to be very significant) in pursuit of its commercial goals, while Roche and especially Merck pursued a more moderate and science-based approach to development of CETP inhibitors. Other companies stopped development of their CETP inhibitors, thus losing their opportunities in this field. Meanwhile, various companies and academic group have been developing other approaches to HDL raising, such as apolipoprotein A1 mimetics, which are in early stages of development.

Despite its early setbacks, HDL-raising drugs may turn out to be a big field after all.

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