2011 ASCO: Exelixis Reports Expanded Cabozantinib (XL184) Phase II Data For Advanced Ovarian Cancer; Six Deaths Reported

Exelixis, Inc. reported expanded Phase 2 study data with respect to cabozantinib (XL184) use in advanced ovarian cancer patients at the recent 2011 American Society of Clinical Oncology Annual Meeting. The overall solid tumor Phase 2 safety and tolerability data reference six deaths, including two ovarian cancer patients.

Ronald J. Buckanovich, M.D., Ph.D., Assistant Professor, Departments of Internal Medicine & Obstetrics and Gynecology, University of Michigan

Exelixis, Inc. reported expanded Phase 2 study data with respect to cabozantinib (XL184) use in advanced ovarian cancer patients at the 2011 American Society of Clinical Oncology (ASCO) Annual Meeting . The overall solid tumor Phase 2 safety and tolerability data refers to six deaths, including two ovarian cancer patients.

On May 19, 2011, we reported promising cabozantinib phase 2 solid tumor (including ovarian) data, which was presented at an ASCO press briefing held in advance of the 2011 ASCO Annual Meeting. As noted in our May 19 article, cabozantinib demonstrated excellent activity against several solid tumors, including ovarian cancer. In addition, we reported that cabozantinib showed promising activity in ovarian cancer patients independent of prior response to platinum drug-based therapies.

Ronald J. Buckanovich, M.D., Ph.D., Assistant Professor, Departments of Internal Medicine & Obstetrics and Gynecology, University of Michigan, presented the expanded cabozantinib Phase 2 data relating to use of the drug in advanced ovarian cancer patients, on June 4 at the 2011 ASCO Annual Meeting.

Ovarian Cancer Patient Population & Overall Response Rate

(Image Source: Exelixis, Inc.)

The cabozantinib trial is an ongoing phase 2 adaptive randomized discontinuation trial. As of the February 11, 2011 cut-off date, accrual in the cabozantinib study cohort was complete at 70 patients.

The 70 patients enrolled in the ovarian cancer cohort received oral cabozantinib (100 mg) daily over a 12 week “Lead-in Stage.” These patients had a minimum follow-up of at least 12 weeks and were thus evaluable for safety and the primary efficacy endpoint of response per RECIST (Response Evaluation Criteria in Solid Tumors).

Patient tumor response was assessed every 6 weeks. Receipt of cabozantinib treatment beyond the 12 week open label Lead-in Stage was based upon patient response: (1) patients with a partial response (PR) or complete response (CR) continued taking cabozantinib, (2) patients with stable disease (SD) were randomized to the cabozantinib treatment arm or the placebo treatment arm (collectively referred to as the “Blinded Randomized Stage”), and (iii) patients with progressive disease (PD) discontinued study treatment. The study primary endpoint was overall response rate (ORR) per RECIST in the Lead-in Stage, and progression free survival (PFS) in the Blinded Randomized Stage. Accrual in any cohort could be halted for high ORR or PD.

Approximately half of the 70 patients enrolled in the cohort were considered platinum drug-refractory/-resistant (49%), defined as a platinum drug-free interval of 6 months or less, and the remainder of patients (51%) had platinum-sensitive disease based on a platinum-free interval greater than 6 months.

The baseline patient tumor histologic characteristics are as follows: serous ovarian cancer (79%), clear cell ovarian cancer (4%), endometrioid ovarian cancer (6%), and other forms of ovarian cancer (11%)

More than half the patients (57%) received 2 or more prior lines of platinum therapy prior to trial enrollment. Some patients also had additional prior lines of therapy with agents such as pegylated liposomal doxorubicin (brand name: Doxil®) or topotecan (brand name: Hycamtin®) (32%), gemcitabine (brand name: Gemzar®) (29%), and VEGF (vascular endothelial growth factor) pathway inhibitors (10%).

Evidence of objective tumor regression was observed in 73% of patients with at least 1 post-baseline medical imaging scan. The best overall response rate per RECIST criteria was 24% (16 PRs and 1 CR). The overall Week-12 disease control rate (DRC = CR + PR + SD) was 53%. The Week-12 DCRs in the platinum drug-refractory, -resistant, and -sensitive groups were 36%, 39%, and 67%, respectively.

Based on an observed high rate of clinical activity, randomization was halted, and randomized patients were unblinded.  At this point, the unblinded randomized patients that were treated with placebo were allowed to “cross-over” to treatment with cabozantinib. Disease stabilization was experienced by some ovarian cancer patients who had progressive disease prior to treatment cross-over.

“These latest results in metastatic ovarian cancer demonstrate the potential broad utility of cabozantinib beyond bone-predominant types of cancers such as castration-resistant prostate cancer. The high rates of durable response with our dual inhibitor of MET and VEGFR2 compare favorably to those of other single-agent targeted therapies and cytotoxic agents in development,” said Michael M. Morrissey, Ph.D., president and chief executive officer of Exelixis. “These results underscore the potential of cabozantinib in metastatic ovarian cancer, and we are in discussions with leading cooperative groups to plan further evaluation of cabozantinib in randomized trials for this indication.”

Activity in Platinum Drug-Sensitive, -Refractory, and -Resistant Disease

Ignace Vergote, M.D., Ph.D., senior author of the cabozantinib (XL184) ASCO presentation & Chairman, Leuven Cancer Institute, University of Leuven, European Union

(Image Source: Exelixis, Inc.)

Two of 11 patients (18%) with platinum refractory disease, defined as a platinum-free interval of <1 month, achieved a confirmed response (1 CR and 1 PR).

In the subset of patients with platinum-resistant disease, defined as a platinum-free interval of 1-6 months, 5 of 23 (22%) achieved a PR.

Ten of 36 patients (28%) with platinum sensitive disease achieved a PR.

A total of 37 patients experienced reductions in the ovarian cancer tumor marker CA-125 (cancer antigen-125), including 8 with decreases greater than 50%. There is no consistent concordance between CA-125 changes and tumor regression. The median duration of response has not yet been reached with 36 weeks of median follow-up.

“The continued activity of cabozantinib in a larger population of ovarian cancer patients is very encouraging, especially with respect to the clinical benefit observed in both platinum-sensitive and platinum-resistant/refractory disease. This activity profile has not been observed with other single-agent TKIs [tyrosine kinase inhibitors], and cabozantinib has the potential to be an important new treatment for ovarian cancer,” said Ignace Vergote, M.D., Ph.D., senior author of the presentation and Chairman of the Leuven Cancer Institute at the University of Leuven, European Union. “The high rate of disease control in platinum-resistant and platinum-refractory disease suggests that cabozantinib may help to address the substantial unmet medical need faced by patients who have sub-optimal responses to platinum-based therapies. I believe that further evaluation will help to define the potential role of cabozantinib in the treatment of ovarian cancer.”

General Safety & Tolerability Data 

Safety data are available for the 70 patients in the Lead-In phase of the cabozantinib study. The most common CTCAE (Common Terminology Criteria for Adverse Eventsgrade 3 or 4 adverse events (AEs), regardless of causality, were diarrhea (10%), fatigue (9%), palmar-plantar erythrodysesthesia  syndrome (also referred as “hand-foot syndrome”)(7%), vomiting (4%), abdominal pain (3%), hypomagnesemia (3%), and nausea, constipation, rash, increased transaminase, and hypertension (each 1%). At least one dose reduction was reported in 37% of patients. Less frequent important medical events, regardless of causality, were hemorrhage (11% all CTCAE grades, 0% CTCAE grade 3 or 4), venous thrombosis (6% all CTCAE grades, 4% CTCAE grade 3 or 4), and gastrointestinal perforation (6% all CTCAE grades, 0% CTCAE grade 3 or 4).

To access the cabozantinib clinical study data information, please visit www.exelixis.com/sites/default/files/pdf/ASCO_2011-XL184-Ovarian.pdf

Six Deaths Reported (Including Two Ovarian Cancer Patients)

If you examine the Exelixis press release dated June 4 (entitled, Exelixis’ Cabozantinib Demonstrates Encouraging Clinical Activity in Patients with Metastatic Ovarian Cancer — Disease control rate of 53% at week 12, response rate of 24%), which addresses data for cabozantinib use in advanced ovarian cancer patients, pay particular attention to the wording under the heading entitled, “Safety and Tolerability.”  Within the wording set forth under that heading, you will find the following statement: “Two cabozantinib-related grade 5 AEs [adverse events], one enterocutaneous fistula and one intestinal perforation, were reported after the Lead-In phase.” Pursuant to the CTCAE guidelines, a “grade 5 adverse event” is defined as “death related to AE [adverse event].”

We should also note that the two ovarian cancer deaths were summarized briefly in the ASCO presentation regarding cabozantinib use in advanced ovarian cancer.

The reporting of all six deaths is set forth in the Exelixis press release, dated June 5, 2011 (entitled, Exelixis’ Cabozantinib Demonstrates Broad Clinical Activity in Multiple Tumor Types), in similar fashion. Within this release, the sentence provided under the heading “Safety and Tolerability” states: “There were 6 (1%) cabozantinib-related grade 5 [adverse] events, all of which were reported after the Lead-In phase of the trial: respiratory compromise (breast cancer), hemorrhage (NSCLC [non-small cell lung cancer]), enterocutaneous perforation (ovarian cancer), intestinal perforation (ovarian cancer), gastrointestinal hemorrhage (pancreatic cancer), and death (CRPC [castrate resistant prostate cancer]).”

Exelixis Chief Executive Michael Morrissey said the safety statistics are consistent with targeted cancer therapies like cabozantinib that block a pathway used by tumor cells to secure blood vessels.

Cowen & Co analyst Eric Schmidt said the rate of cabozantinib treatment-related deaths — 1 percent — was “no different from what we have seen for every other Phase 1 and 2 trials here at ASCO.”

“While drug safety is of less concern in cancer indications than in others, the apparent morbidities associated with cabo[zantinib] use will confound interpretation of clinical benefit in a trial designed to show anything less than overall survival,” Canaccord analyst George Farmer said in a research note.

In a note to investors, Piper Jaffray analyst Edward Tenthoff said: “The company is exploring lower doses, but the concern is that cabo[zantinib] will not retain the impressive efficacy seen to date.”

Mr. Morrissey said Exelixis plans to move forward with the current daily 100 mg dose of the drug.

Dr. Nicholas J. Vogelzang (Director, Comprehensive Cancer Centers of Nevada) Discusses Mortalities in the Cabozantinib (XL184) Trial

Take Away Message

  • Cabozantinib demonstrates promising activity in both platinum drug-sensitive and platinum drug-resistant/-refractory ovarian cancer.
  • Week 12 overall disease control rate of 53%.
  • Response rates of 18% in platinum-refractory, 22% in platinum-resistant and 28% in platinum-sensitive patients.
  • Cabozantinib shows encouraging duration of response.
  • After 36 weeks of follow-up, median duration of response not reached.
  • Tolerability profile is consistent with that of other tyrosine kinase inhibitors (6 solid tumor patient deaths (1% of all solid tumor pts), including 2 ovarian cancer patients (3% of ovarian cancer pts)).
  • Discordant effects observed between CA-125 changes and clinical activity.
  • Simultaneous targeting of MET and VEGFR2 with cabozantinib results in robust effects in patients with advanced ovarian cancer.
  • Non-randomized expansion cohort is currently accruing in platinum-resistant/-refractory ovarian cancer.

About the MET & VEGFR2 Pathways

To learn more about (i) the role of MET in cancer, (ii) the relationship between the MET and VEGFR pathways, and (iii) the dual inhibition of MET and VEGFR2, visit http://www.metinhibition.com/.

About Cabozantinib (XL184)

Cabozantinib (XL184) is a potent, dual inhibitor of MET and VEGFR2. Cabozantinib is an investigational agent that provides coordinated inhibition of metastasis and angiogenesis to kill tumor cells while blocking their escape pathways. The therapeutic role of cabozantinib is currently being investigated across several tumor types. MET is upregulated in many tumor types, thus facilitating tumor cell escape by promoting the formation of more aggressive phenotypes, resulting in metastasis. MET-driven metastasis may be further stimulated by hypoxic conditions (i.e., deprivation of adequate oxygen supply) in the tumor environment, which are often exacerbated by selective VEGF-pathway inhibitors. In preclinical studies, cabozantinib has shown powerful tumoricidal, anti-metastatic and anti-angiogenic effects, including: (i) extensive apoptosis of malignant cells; (ii) decreased tumor invasiveness and metastasis; (iii) decreased tumor and endothelial cell proliferation; (iv) blockade of metastatic bone lesion progression; and (v) disruption of tumor vasculature.

About Exelixis

Exelixis, Inc. is a biotechnology company committed to developing small molecule therapeutics for the treatment of cancer. Exelixis is focusing its resources and development efforts exclusively on cabozantinib, its most advanced solely-owned product candidate, in order to maximize the therapeutic and commercial potential of this compound. Exelixis believes cabozantinib has the potential to be a high-quality, differentiated pharmaceutical product that can make a meaningful difference in the lives of patients. Exelixis has also established a portfolio of other novel compounds that it believes have the potential to address serious unmet medical needs. For more information, please visit the company’s web site at www.exelixis.com

Sources: 

Cabozantinib (XL184) Clinical Trial Information
Related Libby’s H*O*P*E*™ Postings
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PARP Inhibitor MK-4827 Shows Anti-Tumor Activity in First Human Clinical Study

MK-4827, a new drug that targets proteins responsible for helping cancer cells repair their damaged DNA, has shown promising anti-tumor activity in its first human clinical trial.

MK-4827, a new drug that targets proteins responsible for helping cancer cells repair their damaged DNA, has shown promising anti-tumour activity in its first human clinical trial. Some patients with a range of solid tumors, many of whom had been treated unsuccessfully for their cancer with other therapies, have seen their tumors shrink or stabilize for periods of between 46 days to more than a year. The research will be presented today (Thursday) at the 22nd EORTCNCIAACR [1] Symposium on Molecular Targets and Cancer Therapeutics, which is being held in Berlin, Germany.

PARP is a key signaling enzyme involved in triggering the repair of single-strand DNA damage. PARP inhibition has been demonstrated to selectively kill tumor cells lacking components of the homologous recombination (HR) DNA repair pathway while sparing normal cells. Known defects in HR repair include the well-characterized hereditary BRCA1 and BRCA2 mutations in breast and ovarian cancer, as well as nonhereditary BRCA mutations. (Photo Credit: AstraZeneca Oncology)

Laboratory studies of the drug, MK-4827, have shown that it inhibits proteins called PARP1 and PARP2 (poly(ADP)-ribose polymerase). PARP is involved in a number of cellular processes and one of its important functions is to assist in the repair of single-strand breaks in DNA. Notably, if one single-strand DNA break is replicated (replication occurs before cell division), then it results in a double-strand break.  By inhibiting the action of PARP, double-strand breaks occur, which in turn, lead to cell death. Tumors that are caused by a mutation in the BRCA1 or BRCA2 genes are susceptible to cell death through PARP inhibition because correctly functioning BRCA genes assist in repairing double-strand DNA breaks via a process called homologous-recombination-dependent DNA repair, whereas mutated versions are unable to perform this role. Normal cells do not replicate as often as cancer cells and they still have homologous repair operating; this enables them to survive the inhibition of PARP and makes PARP a good target for anti-cancer therapy.

In a Phase I trial [2] conducted at the H. Lee Moffitt Cancer Center (Tampa Florida, USA), University of Wisconsin-Madison (Madison, USA) and the Royal Marsden Hospital (London, UK), MK-4827 was given to 59 patients (46 women, 13 men) with a range of solid tumors such as non-small cell lung cancer (NSCLC), prostate cancer, sarcoma, melanoma and breast and ovarian cancers. Some patients had cancers caused by mutations in the BRCA1/2 genes, such as breast and ovarian cancer, but others had cancers that had arisen sporadically.

Robert M. Wenham, M.D., MS, FACOG, Clinical Director, Gynecologic Oncology, Department of Women's Oncology, H. Lee Moffitt Cancer Center

The drug was given in pill form once a day, and the researchers found that the maximum tolerated dose was 300 mg per day. Dr. Robert Wenham, Clinical Director for Gynecologic Oncology in the Department of Women’s Oncology at the Moffitt Cancer Center, who is presenting data on behalf of the participating investigators, said: “MK-4827 is generally well tolerated, with the main dose-limiting toxicity being thrombocytopenia – an abnormal decrease in the number of platelets in the circulatory blood. The most common side effects are mild nausea, vomiting, anorexia and fatigue.”

The researchers saw anti-tumor responses in both sporadic (non-inherited) and BRCA1/2 mutation-associated cancers [emphasis added]. Ten patients with breast and ovarian cancers had partial responses, with progression-free survival between 51-445 days, and seven of these patients are still responding to treatment. Four patients (two with ovarian cancer and two with NSCLC) had stable disease for between 130-353 days.

Dr. Wenham said: “Most patients in the trial had exhausted standard therapies and those who responded to this drug have benefited. Several patients have been receiving treatment for more than a year. The responses mean that MK-4827 is working as hoped and justify additional studies. Just how well MK-4827 works compared to other treatments is the goal of the next set of studies.”

He gave a possible explanation as to why patients with cancers that were not caused by BRCA1 or BRCA 2 gene mutations also responded to the PARP inhibition. “BRCA is a tumor suppressor gene that assists in repairing double stranded DNA breaks. In BRCA-mutation related cancers, loss of both copies of the gene results in a non-functional protein and thus BRCA deficiency. Because BRCA works with other proteins, BRCA-pathway related deficiency can be seen in the absence of two mutated copies of the BRCA genes. This may explain why responses have been reported for this class of drugs in non-BRCA mutant cancers.”

Dr. Wenham and his colleagues are recruiting more patients for additional studies and an expansion of the existing trial. “We want to understand what types of cancers will respond best to treatment with MK-4827,” he said. “Cohorts are currently open for patients with ovarian cancer, patients without germ-line BRCA mutations, and prostate cancer patients. Cohorts will open soon for patients with T-cell prolymphocytic leukemia, endometrial cancer, breast cancer and colorectal cancer. MK-4827 is also being studied in combination with conventional chemotherapy drugs.”

Sources:

Additional Information:

Related Information:

References:

[1] EORTC [European Organisation for Research and Treatment of Cancer, NCI [National Cancer Institute], AACR [American Association for Cancer Research].

[2] This study was funded by Merck & Co., Inc. MK-4827 is owned by Merck & Co., Inc.

PI3K Pathway: A Potential Ovarian Cancer Therapeutic Target?

…[T]here are several PI3K signaling pathway targeting drugs in clinical development for use against ovarian cancer and solid tumors, including GDC-0941, BEZ235, SF1126, XL-147, XL-765, BGT226, and PX-866.  The results of two recent medical studies suggest that the use of PI3K-targeted therapies may offer an effective therapeutic approach for patients with advanced-stage and recurrent ovarian cancer, including a generally chemotherapy-resistant histological subtype of epithelial ovarian cancer known as “ovarian clear cell cancer” (OCCC).  The targeting of the PI3K pathway in endometrial, ovarian, and breast cancer is also being investigated by a Stand Up To Cancer “Dream Team.” …

PI3K Cellular Signaling Pathway — An Overview

PI3K/AKT cellular signaling pathway (Photo: Cell Signaling Technology(R))

In 2004 and 2005, multiple researchers identified mutations in the PIK3CA  gene with respect to multiple cancers.[1]  The PIK3CA gene encodes the PI3K catalytic subunit p110α. PI3K (phosphoinositide 3- kinase) proteins have been identified in crucial signaling pathways of ovarian cancer cells. PI3Ks are also part of the PI3K-AKT-mTOR signaling pathway which promotes cellular glucose metabolism, proliferation, growth, survival, and invasion and metastasis in many cancers. PIK3CA gene mutations can increase PI3K signaling, thereby activating the PI3K-AKT-mTOR pathway within cancer cells.

As of this writing, there are several PI3K signaling pathway targeting drugs in clinical development for use against ovarian cancer and solid tumors, including GDC-0941, BEZ235, SF1126, XL-147, XL-765, BGT226, and PX-866. [2]  The results of two recent medical studies suggest that the use of PI3K-targeted therapies may offer an effective therapeutic approach for patients with advanced-stage and recurrent ovarian cancer, including a generally chemotherapy-resistant histological subtype of epithelial ovarian cancer known as “ovarian clear cell cancer” (OCCC).  The targeting of the PI3K pathway in endometrial, ovarian, and breast cancer is also being investigated by a Stand Up To CancerDream Team.”

Frequent Mutation of PIK3CA Gene In Recurrent & Advanced Clear Cell Ovarian Cancer

OCCC is one of the five major subtypes of epithelial ovarian cancer. OCCC accounts for only 4% to 12% of epithelial ovarian cancer in Western countries and, for unknown reasons, it comprises more than 20% of such cancers in Japan [3,4,5]. OCCC possesses unique clinical features such as a high incidence of stage I disease, a large pelvic mass, an increased incidence of venous thromboembolic complications, and hypercalcemia. It is frequently associated with endometriosis.  Compared to serous ovarian cancer, OCCC is relatively resistant to conventional platinum and taxane-based chemotherapy. For these reasons, new effective therapies are desperately needed for OCCC.

Researchers from Johns Hopkins and the University of California, Los Angeles (UCLA) analyzed 97 OCCC tumors for genetic sequence mutations in KRAS (v-Ki-ras2 Kirsten rat sarcoma viral oncogene homolog), BRAF (v-raf murine sarcoma viral oncogene homolog B1), PIK3CA (phosphoinositide-3-kinase, catalytic, alpha polypeptide), TP53 (tumor protein p53), PTEN (phosphatase and tensin homolog), and CTNNB1 (Catenin, Beta-1) as these mutations frequently occur in other major types of ovarian cancers.[6] The samples tested included the following:

  • 18 OCCCs for which affinity-purified tumor cells from fresh specimens were available;
  • 10 OCCC tumor cell lines.

Upon test completion, the researchers discovered that sequence mutations of PIK3CA, TP53, KRAS, PTEN, CTNNB1, and BRAF occurred in 33%, 15%, 7%, 5%, 3%, and 1% of OCCC cases, respectively.

Clear cell carcinoma of the ovary (Photo: Geneva Foundation For Medical Education & Research)

The sequence analysis of the 18 affinity purified OCCC tumors and the 10 OCCC cell lines showed a PIK3CA mutation frequency of 46%. Based upon these findings the researchers concluded that the use of PIK3CA-targeting drugs may offer a more effective therapeutic approach compared with current chemotherapeutic agents for patients with advanced-stage and recurrent OCCC. As noted above, there are several PI3K-targeting drugs in clinical development for use against ovarian cancer and solid tumors.[2]

Notably, one of the researchers involved with this OCCC study is Dennis J. Slamon, M.D., Ph.D. Dr. Slamon serves as the Director of Clinical/Translational Research, and as Director of the Revlon/UCLA Women’s Cancer Research Program at the Jonsson Comprehensive Cancer Center. Dr. Slamon is also a professor of medicine, chief of the Division of Hematology/Oncology and Executive Vice Chair of Research for UCLA’s Department of Medicine. Dr. Slamon is a co-discoverer of the breast cancer drug Herceptin®. Herceptin is a monoclonal antibody targeted therapy used against HER-2 breast cancer, an aggressive breast cancer subtype that affects 20% to 30% of women with the disease. Herceptin’s development was based, in part, upon the unique genetic profile of HER-2 breast cancer as compared to other forms of breast cancer. Herceptin® revolutionized the treatment of HER-2 postive breast cancer and is recognized worldwide as the standard of care for that subtype of breast cancer.  The approach taken by Johns Hopkins and UCLA researchers in this study — the identification of  a subtype within a specific form of cancer that may be susceptible to a targeted therapy —  bears a striking similarity to the overarching approach taken in the development of Herceptin®.

Ovarian Cancer & Other Solid Tumors With PIK3CA Gene Mutations Respond To PI3K-AKT-mTOR Pathway Inhibitors In Phase I Clinical Testing.

Testing patients with cancer for PIK3CA gene mutations is feasible and may allow targeted treatment of the PI3K-AKT-mTOR cellular signaling pathway, according to the results of a University of  Texas, M.D. Anderson Cancer Center study presented on November 17, 2009 at the 2009 AACR (American Association for Cancer Research)-NCI (National Cancer Institute)-EORTC (European Organization For Research & Treatment of Cancer) International Conference on Molecular Targets and Cancer Therapeutics.[7]

mTOR cellular signaling pathway (Photo: Cell Signaling Technology(R))

Filip Janku, M.D., Ph.D, a clinical research fellow with the M.D. Anderson Cancer Center’s department of investigational cancer therapeutics, and colleagues conducted a mutational analysis of exon 9 and exon 20 of the PI3KCA gene using DNA from the tumors of patients referred to targeted therapy clinical trials. Patients with PIK3CA mutations were preferably treated whenever possible with regimens utilizing PI3K-AKT-mTOR signaling pathway inhibitors.

As part of this study 117 tumor samples were analyzed. PIK3CA mutations were detected in 14 (12%) patients.  In tumor types with more than 5 patients tested, PIK3CA mutations were identified in endometrial cancer (43%, 3 out of 7 patients), ovarian cancer (22%, 5 out of 23 patients), squamous head and neck cancer (14%, 1 out of 7 patients), breast cancer (18%, 2 out of 11 patients), and colon cancer (15%, 2 out of 13 patients). No mutations were identified in patients with melanoma or cervical cancer.

Of the 14 patients found to possess PIK3CA mutations, 10 were treated based upon a clinical trial protocol that included a drug targeting the PI3K-AKT-mTOR pathway.  A partial response to treatment was experienced by 4 (40%) patients. Although the total number of patients is small, there were 2 (67%) patient responses in 3 endometrial cancer cases, 1 (25%) patient response in 4 ovarian cancer cases, 1 (100%) patient response in 1 breast cancer, and no patient response in 1 colorectal cancer case.  Although the total number of study patients is small, the researchers conclude that the response rate appears high (40%) in tumors with PIK3CA mutations treated with PI3K-AKT-mTOR pathway inhibitors.

“The implications of this study are twofold,” said Dr. Janku.  “We demonstrated that PIK3CA testing is feasible and may contribute to the decision-making process when offering a patient a clinical trial. Although this study suffers from low numbers, the response rate observed in patients treated with inhibitors of PI3K/AKT/mTOR pathway based on their mutational status was well above what we usually see in phase-1 clinical trials.”  “These results are intriguing but at this point should be interpreted with caution,” said Janku. “The promising response rate needs to be confirmed in larger groups of patients. We expect to learn more as this project continues to offer PIK3CA screening to patients considering a phase-1 clinical trial.”

Stand Up 2 Cancer Dream Team: Targeting the PI3K Pathway in Women’s Cancers

The potential importance of the PI3K pathway in the treatment of ovarian cancer is emphasized by the two medical studies above.  This issue is also receiving considerable attention from one of the Stand Up 2 Cancer (SU2C) “Dream Teams,” which is going to evalute  the potential for targeting the PI3K pathway in women’s cancer.  SU2C assigned $15 million of cancer research funding to this critical issue.  The scientists involved in this SU2C Dream Team are the pioneers who discovered the PI3K pathway and validated its role in human cancers, and they will focus on breast, ovarian and endometrial cancers, all of which possess the PI3K mutation.

The leader and co-leaders of the PI3K pathway SU2C team are set forth below.

Leader:

Lewis C. Cantley, Ph.D., Director, Cancer Center at Beth Israel Deaconess Medical Center.

Co-Leaders:

Charles L. Sawyers, M.D., Director, Human Oncology and Pathogenesis Program, Memorial Sloan-Kettering Cancer Center.

Gordon B. Mills, M.D., Ph.D., Chair, Department of Systems Biology, University of Texas, M.D. Anderson Cancer Center.

The specific SU2C Dream Team research goal with respect to targeting the PI3K pathway in women’s cancers is stated as follows:

The PI3K pathway is mutated in more cancer patients than any other, and these mutations are the most frequent events in women’s cancers, making it an attractive molecular target for agents that inhibit these genetic aberrations. If successful, this project will allow clinicians to use biomarkers and imaging techniques to predict which patients will benefit from PI3K pathway inhibitors and lead to the development of therapeutic combinations that will hit multiple targets in the complex pathways that contribute to cancer cell growth.  This work will help assure that these therapies are given to patients who will benefit from them, and it will also increase the overall pace of clinical trials targeting PI3K inhibitors.

Based upon the two studies discussed, and the creation and funding of the SU2C Dream Team for the purpose of targeting the PI3K pathway in women’s cancer, the future holds great promise in the battle against ovarian cancer (including OCCC).  It is our hope that more clinical study investigators will offer PI3K pathway mutation screening to all ovarian cancer patient volunteers.  Libby’s H*O*P*E*™ will continue to monitor the clinical development of PI3K pathway inhibitors, and make our readers aware of all future developments.

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References:

1/Yuan TL, Cantley LC. PI3K pathway alterations in cancer: variations on a theme. Oncogene. 2008 Sep 18;27(41):5497-510. PubMed PMID: 18794884
Samuels Y, Ericson K. Oncogenic PI3K and its role in cancer. Curr Opin Oncol. 2006 Jan;18(1):77-82. PubMed PMID: 16357568.
Levine DA, Bogomolniy F, Yee CJ, et. al. Frequent mutation of the PIK3CA gene in ovarian and breast cancers. Clin Cancer Res. 2005 Apr 15;11(8):2875-8. PubMed PMID: 15837735.
Samuels Y, Wang Z, Bardelli A, et. al. High frequency of mutations of the PIK3CA gene in human cancers. Science. 2004 Apr 23;304(5670):554. Epub 2004 Mar 11. PubMed PMID: 15016963.

2/For open ovarian cancer clinical trials using a PI3K-targeted therapy; CLICK HERE; For open solid tumor clinical trials using a PI3K-targeted therapy, CLICK HERE.

3/ Itamochi H, Kigawa J & Terakawa N.  Mechanisms of chemoresistance and poor prognosis in ovarian clear cell carcinoma. Can Sci 2008 Apr;99(4):653-658. [PDF Document]

4/Schwartz DR, Kardia SL, Shedden KA, et. alGene Expression in Ovarian Cancer Reflects Both Morphology and Biological Behavior, Distinguishing Clear Cell from Other Poor-Prognosis Ovarian CarcinomasCan Res 2002 Aug; 62, 4722-4729.

5/Sugiyama T & Fujiwara K.  Clear Cell Tumors of the Ovary – Rare Subtype of Ovarian Cancer, Gynecologic Cancer, American Society of Clinical Oncology (ASCO) Educational Book, 2007 ASCO Annual Meeting, June 2, 2007 (Microsoft Powerpoint presentation).

6/Kuo KT, Mao TL, Jones S, et. al. Frequent Activating Mutations of PIK3CA in Ovarian Clear Cell Carcinoma. Am J Pathol. 2009 Apr 6. [Epub ahead of print]

7/Janku F, Garrido-Laguna I, Hong D.S.  PIK3CA mutations in patients with advanced cancers treated in phase I clinical trials, Abstract #B134, Molecular Classification of Tumors, Poster Session B, 2009 AACR-NCI-EORTC Molecular Targets and Cancer Therapeutics Conference. [PDF Document].

Medicare Expands Coverage of PET Scans as Cancer Diagnostic Tool

“The Centers for Medicare & Medicaid Services (CMS) issued a final national coverage determination (NCD) to expand coverage for initial testing with positron emission tomography (PET) for Medicare beneficiaries who are diagnosed with and treated for most solid tumor cancers.  This decision applies to PET scans used to support initial diagnosis and treatment for most types of solid tumor cancers. … It also expands coverage of PET scans for subsequent follow up testing in beneficiaries who have cervical or ovarian cancer … A minimally invasive diagnostic imaging procedure, PET uses a radioactive tracer to evaluate glucose metabolism in tumors and in normal tissue. …”

“For Immediate Release: Monday, April 06, 2009
Contact: CMS Office of Public Affairs
202-690-6145

MEDICARE EXPANDS COVERAGE OF PET SCANS AS CANCER DIAGNOSTIC TOOL

CMS’ Coverage with Evidence Development Project Shows PET Scans as “Reasonable and Necessary” for Initial Treatment Decisions of Most Solid Tumor Cancers

Centers For Medicare & Medicaid Services

Centers For Medicare & Medicaid Services

The Centers for Medicare & Medicaid Services (CMS) issued a final national coverage determination (NCD) to expand coverage for initial testing with positron emission tomography (PET) for Medicare beneficiaries who are diagnosed with and treated for most solid tumor cancers.

This NCD removes a clinical study requirement for PET scan use in these patients.

Since 2005, Medicare coverage of PET scans for diagnosing some forms of cancer and guiding treatment has been tied to a requirement that providers collect clinical information about how the scans have affected doctors’ treatment decisions. This information was gathered through the National Oncologic PET Registry (NOPR) observational study. This decision removes the requirement to report data to the NOPR when the PET scan is used to support initial treatment (or diagnosis and “staging“) of most solid tumor cancers.

Medicare collects data from the NOPR under CMS’ Coverage with Evidence Development (CED) program. CED allows Medicare to develop evidence about how a medical technology is used in clinical practice so that Medicare can do the following:

(a) clarify the impact of these items and services on the health of Medicare beneficiaries;

(b) consider future changes in coverage for the technology; and

(c) generate clinical information that will improve the evidence base upon which providers base their recommendations to Medicare beneficiaries regarding the technology.

This decision is based, in part, on the information generated as a result of CMS’ 2005 decision to require NOPR reporting for many cancer PET scans. As a result of this evidence from NOPR, CMS reconsidered its 2005 coverage policy. This decision is the first time that CMS has reconsidered a coverage policy based on new evidence developed under the CED program.

‘This expansion in coverage for PET scans shows that the Coverage with Evidence Development program is a success,’ said CMS Acting Administrator Charlene Frizzera. ‘CED allowed us to cover an emerging technology, learn more about its usage in clinical practice, and adjust our coverage policies accordingly. Thanks to CED, Medicare beneficiaries have greater access to cutting edge medical technologies and treatments.’

Positron Emission Tomography (PET) equipment (Photo Source:  www.RadiologyInfo.org)

Positron Emission Tomography (PET) equipment (Photo Source: RadiologyInfo.org)

This decision applies to PET scans used to support initial diagnosis and treatment for most types of solid tumor cancers. It also expands coverage of PET scans for subsequent follow up testing in beneficiaries who have cervical or ovarian cancer, or who are being treated for myeloma, a cancer that affects white blood cells. For these cancers, NOPR data collection will no longer be required. [Emphasis added by Libby’s H*O*P*E*™]

It is important to note that today’s decision still requires clinicians to report data to the NOPR when using PET scans to monitor the progress of treatment or remission of cancer in some cases. Although the evidence generated by the NOPR study helped CMS determine that PET scans are useful in helping guide treatment when cancer is first diagnosed, scientific evidence is not as strong in showing that PET scans are as useful in making subsequent treatment decisions for some types of cancer.

A minimally invasive diagnostic imaging procedure, PET uses a radioactive tracer to evaluate glucose metabolism in tumors and in normal tissue. The test may provide important clinical information to guide the initial treatment approach (e.g., diagnosis and “staging”) for many cancers.

This additional information may help physicians to distinguish benign from cancerous lesions and better determine the extent of a tumor’s growth or metastasis. PET scans have also been used in subsequent testing for cancer patients, e.g., to monitor cancer progression or remission after cancer treatment has begun.

More information about the types of cancer covered by this new policy is available in CMS’ final decision memorandum. …”

SourceMedicare Expands Coverage of PET Scans As Cancer Diagnostic Tool – CMS’ Coverage with Evidence Development Project Shows PET Scans as “Reasonable and Necessary” for Initial Treatment Decisions of Most Solid Tumor Cancers, Centers for Medicare & Medicaid Services, Press Release, April 6, 2009.

Secondary Sources:

Comment:  The CMS Decision Memo involving the use of PET scans for solid tumors allows an ovarian cancer patient (who is a Medicare beneficiary) to obtain a PET scan for “initial treatment strategy” purposes.  “Initial Treatment Strategy” is generally defined by CMS as encompassing initial diagnosis or staging.  An ovarian cancer patient (who is a Medicare beneficiary) can also obtain a PET scan for “subsequent treatment strategy” purposes.  “Subsequent Treatment Strategy” is generally defined by CMS as encompassing “restaging” and “monitoring response to treatment when a change in treatment is anticipated.”

New Vascular Disrupting Agent In Combination With Avastin Produces a 64% Disease Stabilization Rate in a Small Phase I Solid Tumor Clinical Trial

In solid tumors, [vascular disrupting agents] VDA’s, such as ZYBRESTAT™, rapidly disrupt the vasculature within the tumor, reduce blood-flow, and deprive the tumor of oxygen and nutrients, resulting in tumor cell death. This disruption of the newly formed blood vessels contrasts with the action of anti-angiogenic therapies (e.g., bevacizumab/Avastin™), which are designed to prevent new blood vessel formation. … Specifically, Zybrestat™ was tested on advanced solid malignancies in Phase I clinical trial involving 14 patients. … Nine of fourteen patients experienced disease stabilization for greater than 12 weeks. Three patients experienced disease stabilization for greater than 24 weeks, with two of these patients continuing with stable disease at 47 and 29 weeks, respectively.

Based upon an abstract presentation made at the 2008 American Society of Clinical Oncology (ASCO) Annual Meeting recently held in Chicago on May 30th through June 3rd, the new vascular disrupting agent (VDA) Zybrestat™ (fosbretabulin) produced an advanced solid tumor disease stabilization rate of 64 percent.

Vascular disruption represents a new approach to a validated therapeutic strategy: depriving tumors of blood supply. In solid tumors, VDA’s, such as ZYBRESTAT™, rapidly disrupt the vasculature within the tumor, reduce blood-flow, and deprive the tumor of oxygen and nutrients, resulting in tumor cell death. This disruption of the newly formed blood vessels contrasts with the action of anti-angiogenic therapies (e.g., bevacizumab/Avastin™), which are designed to prevent new blood vessel formation. OXiGENE Inc. (OXiGENE) believes its VDA product candidates may offer advantages over current anti-angiogenic drugs, including superior efficacy and reduced side-effects.

In addition, there is a strong scientific rationale for combining VDA and anti-angiogenesis therapies. OXiGENE and its scientific collaborators have published preclinical research results showing that the combination of OXiGENE VDAs and certain anti-angiogenic drugs (i.e., monoclonal antibodies targeting vascular endothelial growth factor, or VEGF) have synergistic anti-tumor effects. Building upon these results, OXiGENE has undertaken the first-ever human clinical trial of a VDA (ZYBRESTAT) in combination with an anti-angiogenic agent (bevacizumab / AVASTIN.) The additional benefits of vascular disrupting agents include:

  • This method of treatment is designed to target newly formed abnormal blood vessels, rather than the established blood vessels found in healthy tissue, resulting in fewer side effects in the oncology setting than conventional disease treatments such as radiation and chemotherapy. VDAs are designed to address the complete spectrum of solid tumors, whereas other approaches, which directly target tumor cells, require the development of different drugs for different types of solid tumors.
  • VDAs are designed to target endothelial cells associated with new blood vessel formation, so drug resistant mutations are unlikely to occur.
  • Damaging one or two blood vessels can cause thousands of tumor cells to die.
  • The ability of VDAs to selectively target newly formed or abnormal blood vessels makes them well-suited for certain ocular diseases, such as age-related macular degeneration, in which the formation of new, abnormal blood vessels in the eye plays a key role in disease.

Specifically, Zybrestat™ was tested on advanced solid malignancies in Phase I clinical trial involving 14 patients. The patients were divided into three separate dosage cohorts, representing 45mg/m2 (cohort 1), 54mg/m2 (cohort 2) or 63mg/m2 (cohort 3) of Zybrestat™ every 14 days followed by bevacizumab (Avastin™) at a dosage of 10mg/kg four hours later. The study results indicated two grade 3/4 drug dosage limiting toxicities. Nine of fourteen patients experienced disease stabilization for greater than 12 weeks. Three patients experienced disease stabilization for greater than 24 weeks, with two of these patients continuing with stable disease at 47 and 29 weeks, respectively. Dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) showed statistically significant reductions in tumor perfusion/vascular permeability which reversed when Zybrestat™ was used as a monotherapy, but were sustained following the use of bevacizumab (Avastin™). The clinical trial investigators concluded that Zybrestat™ was safe and tolerable at the three dosage levels used, and noted that Zybrestat™ induced profound vascular changes in the solid tumor which were maintained by the presence of bevacizumab (Avastin™).

Sources:

Comment: ZYBRESTAT™ has broad potential therapeutic utility across a wide range of different solid tumor types, and can potentially be combined with mainstay oncology treatment modalities: chemotherapy, radiation therapy and newer, “molecularly-targeted therapies,” such as tumor angiogenesis inhibitors. Preclinical studies have demonstrated that ZYBRESTAT™ has synergistic or additive effects when incorporated in various combination regimens with all of these treatment modalities. There is a strong scientific rationale for combining ZYBRESTAT™ and tumor angiogenesis inhibiting drugs, and ZYBRESTAT™ is the first VDA to be tested in humans in combination with a tumor-angiogenesis-inhibiting drug (bevacizumab / AVASTIN®).