Exelixis Reports Promising Interim Data From Ovarian Cancer Patients Treated With XL184

Exelixis reports promising interim data from ovarian cancer patients treated with XL184, including:  a  32% confirmed response rate per RECIST in patients with platinum-resistant or platinum-sensitive disease, and a 64% overall week-12 disease control rate.

Ignace Vergote, M.D., Ph.D., Head, Department of Obstetrics & Gynecology and Gynecologic Oncology, Catholic University Hospital, Leuven, Belgium

Exelixis, Inc.  today reported interim data from the cohort of patients with advanced epithelial ovarian cancer, primary peritoneal, or fallopian tube carcinoma treated with XL184 in an ongoing phase 2 adaptive randomized discontinuation trial (RDT) [1]. Ignace Vergote, M.D., Ph.D., Head of the Department of Obstetrics and Gynecology and Gynecologic Oncology at the Catholic University Hospital Leuven, Leuven, Belgium, will present the data in the Molecular-Targeted Therapies-Clinical Trials poster session (Abstract #407) on Thursday, November 18th, at the 22nd EORTC-NCI-AACR [2] Symposium on Molecular Targets and Cancer Therapeutics, being held in Berlin, Germany.

XL184 Activity in Patients with Ovarian Cancer

XL184 is an oral, potent inhibitor of MET, VEGFR2 and RET. MET overexpression has been observed in advanced ovarian cancer, and anti-VEGF pathway agents have shown clinical benefit in ovarian cancer patients. For these reasons, co-targeting of the MET and VEGF signaling pathways using XL184 may represent a promising treatment strategy.

As of the November 1, 2010 cut-off date, a total of 51 patients were enrolled into the ovarian cancer cohort, with 31 evaluable for response, and 41 evaluable for safety. The median number of prior systemic treatments was 2. Tumor shrinkage was observed in 30 of 37 (81%) patients with measurable metastatic lesions. Of 31 patients evaluable for response per RECIST (Response Evaluation Criteria In Solid Tumors), 10 (32%) achieved a confirmed partial response (PR). Stable disease (SD) was reported in 15 patients (48%) including 3 patients who achieved unconfirmed PRs. The overall week-12 disease control rate (DCR)(complete responses + partial responses + stable disease responses = DCR) was 64%.

Upon subset analysis, 5 of 17 platinumrefractory or –resistant patients (29%) evaluable for response per RECIST achieved a confirmed PR. SD was reported in 7 patients (41%) including 2 patients with unconfirmed PRs. The week-12 DCR was 59% in platinum-resistant/refractory patients. Durable responses have been observed, including 2 patients with platinum-refractory or resistant disease who remain on study for 34+ and 36+ weeks, and 3 patients with platinum-sensitive disease on study for 24, 24+, and 28+ weeks. Some patients have experienced reductions in the ovarian cancer blood marker CA125, but in general no clear concordance between CA125 changes and tumor shrinkage has been observed.

Safety data are available for 49 patients who had at least 6 weeks of follow-up. The most common grade greater-than or equal to 3 adverse events, regardless of causality were PPE (Palmar-Plantar Erythrodysesthesia) syndrome (also referred to as “hand-foot syndrome”) (12%), diarrhea (7%), fatigue, vomiting (each 5%), nausea, rash, abdominal pain, hypertension, and hypomagnesemia (each 2%).

“The activity of XL184 in women with both platinum-sensitive and platinum-resistant/refractory disease is unique and encouraging. The response rate and overall disease control rate of this oral agent are impressive especially in the group of patients with platinum refractory/resistant ovarian cancer, and compare favorably to other targeted and systemic agents in development,” said, Dr. Vergote. “I believe these encouraging data warrant further evaluation of XL184 in ovarian cancer.”

Michael M. Morrissey, Ph.D., President & Chief Executive Officer, Exelixis, Inc.

“The high response rate in patients with ovarian cancer is reflective of the broad anti-tumor activity of XL184 observed in multiple tumor types to date,” said Michael M. Morrissey, Ph.D., president and chief executive officer of Exelixis. “The data from the RDT underscore the novel and differentiated clinical activity of XL184 in diverse tumor indications with predominance of either soft tissue or bone involvement.”

To access the clinical data poster mentioned in this press release, please visit www.exelixis.com.

Broad Clinical Activity of XL184 – Randomized Discontinuation Trial

XL184 has demonstrated anti-tumor activity in 9 of 12 indications studied to date. In ongoing trials, compelling activity has been observed in medullary thyroid cancer, glioblastoma, and clear cell renal cancer. In the RDT, XL184 is being evaluated in nine different tumor types, with clear signals of activity in six: prostate, ovarian, hepatocellular, breast, non-small cell lung cancer and melanoma. The adaptive RDT design allowed for rapid simultaneous assessment of the activity of XL184 across nine different tumor indications. As of the November 1, 2010 cut-off date, a total of 397 patients have been enrolled into the nine disease-specific cohorts, with 273 evaluable for response, and 312 evaluable for safety. Of 273 patients evaluable for response per RECIST, 39 achieved a PR (either confirmed or unconfirmed) and 100 had SD at week 12. The week-12 DCR for the overall population was 49%, with the highest rates occurring in hepatocellular cancer (75%), castration-resistant prostate cancer (71%), ovarian cancer (64%), melanoma (45%), non-small cell lung cancer (42%) and breast cancer (42%). Of note, a breast cancer patient with evidence of bone metastasis on bone scan demonstrated evidence of resolution on bone scan accompanied by 29% reduction in tumor size. XL184 has been generally well tolerated with a consistent adverse event profile across the nine different RDT tumor types.

About XL184

XL184, an inhibitor of tumor growth, metastasis and angiogenesis, simultaneously targets MET and VEGFR2, key kinases involved in the development and progression of many cancers, including ovarian cancer. It has recently been shown in preclinical models that treatment with selective inhibitors of VEGF signaling can result in tumors that are more invasive and aggressive compared to control treatment. In preclinical studies, upregulation of MET has been shown to occur in concert with development of invasiveness after selective anti-VEGF therapy, and may constitute a mechanism of acquired or evasive resistance to agents that target VEGF signaling. Accordingly, treatment with XL184 in similar preclinical studies resulted in tumors that were less invasive and aggressive compared to control or selective anti-VEGF treatment. Therefore, XL184 has the potential for improving outcomes in a range of indications, including those where selective anti-VEGF therapy has shown minimal or no activity.

About Exelixis

Exelixis, Inc. is a development-stage biotechnology company dedicated to the discovery and development of novel small molecule therapeutics for the treatment of cancer. The company is leveraging its biological expertise and integrated research and development capabilities to generate a pipeline of development compounds with significant therapeutic and commercial potential for the treatment of cancer. Currently, Exelixis’ broad product pipeline includes investigational compounds in phase 3, phase 2, and phase 1 clinical development. Exelixis has established strategic corporate alliances with major pharmaceutical and biotechnology companies, including Bristol-Myers Squibb Company, sanofi-aventis, GlaxoSmithKline, Genentech (a wholly owned member of the Roche Group), Boehringer Ingelheim, and Daiichi-Sankyo. For more information, please visit the company’s web site at http://www.exelixis.com.

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1/Rosner GL, Stadler W, Ratain MJ. et. al.  Randomized discontinuation design: Application to cytostatic antineoplastic agents. J Clin Oncol 20:4478-4484, 2002.  Pursuant to this design, all patients receive the investigational drug for an initial period of time. Patients with standard radiologic tumor shrinkage within that timeframe would continue investigational therapy, while those with radiologic progression or unacceptable toxicity would discontinue therapy. All patients with radiologic stable disease after the initial therapy period are then randomized to continuing or discontinuing therapy in a double-blind placebo-controlled manner. This is an enrichment strategy in which patients with the end point of interest are preferentially enrolled in the randomized portion and in which the heterogeneity of the randomized population is decreased. These two factors result in an increased power for detecting a clinically relevant difference and decrease the number of patients exposed to placebo. Importantly, the enrichment is driven by the properties of the investigational drug as opposed to clinical prognostic factors identified in historical untreated patients or patients treated with a different class of agents. In addition, the statistical behavior of the trial is not highly dependent on investigators’ assumptions regarding the “no dose effect” (i.e., non-receipt of drug = no effect)  for time to progression or stable disease rate, and thus effectively deals with uncertainty in this variable. Finally, patients may find such a trial design more appealing, resulting in brisk accrual.

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

PARP Inhibitor Olaparib Benefits Women With Inherited Ovarian Cancer Based Upon Platinum Drug Sensitivity

Olaparib (AZD2281), a new type of cancer drug known as a “PARP inhibitor,” produced promising results in patients with platinum-refractory, platinum-resistant, and platinum-sensitive ovarian cancer linked to an inherited BRCA1 or BRCA2 gene mutation.

A new type of cancer drug — known as a “PARP inhibitor” — produced promising results in patients with ovarian cancer linked to an inherited BRCA1 or BRCA2 gene mutation. The trial results were published online in the Journal of Clinical Oncology on April 19th.

Scientists at The Institute of Cancer Research (ICR) and The Royal Marsden Hospital, working with pharmaceutical company KuDOS Pharmaceuticals, now a subsidiary of AstraZeneca, found the experimental drug olaparib shrank or stabilized tumors in approximately half of ovarian cancer patients possessing BRCA1 or BRCA2 mutations.

The five-year survival rate for ovarian cancer is just 40 per cent as the majority of patients are diagnosed with an advanced form of the disease. Most patients initially respond well to radical surgery and platinum and taxane-based chemotherapy, but relapse after an average of 18 months. Subsequent treatments generally become less effective as patients build up resistance.

Professor Stan Kaye, Head of Section of Medicine, Institute of Cancer Research; Head of Drug Development Unit, The Royal Marsden Hospital; and Cancer Research UK-funded scientist

“There is an urgent need to find new drugs for women diagnosed with ovarian cancer,” says Professor Stan Kaye, Head of the Section of Medicine at the ICR and Head of the Drug Development Unit at The Royal Marsden Hospital and a Cancer Research UK-funded scientist. “Olaparib is still in early-stage testing but the results so far are very encouraging. These findings raise the possibility that carefully selected patients in future may well be offered olaparib as an alternative to chemotherapy during the course of their treatment.”

Between 2005 and 2008, about 50 women with confirmed or suspected BRCA1 or BRCA2 mutations began treatment with olaparib in a dose escalation and single-stage expansion of a Phase I trial. Twenty patients responded with their tumors shrinking or with significant falls in their ovarian cancer marker CA125, or both. The disease also stabilized in three patients. The drug was effective for an average of seven months. Notably, several patients are still taking olaparib (for nearly two years). Drug side-effects were generally mild, especially when compared to current chemotherapy treatments.

Olaparib is a new type of drug known as a PARP inhibitor that works by turning a tumor’s specific genetic defect against itself. In susceptible cells, olaparib prevents the repair of naturally occurring breaks in DNA, which healthy cells are able to repair. Susceptible cancer cells – those with an existing defect in a DNA repair pathway caused by a mutation in the BRCA1 or BRCA2 genes – are unable to repair themselves, and therefore, die.

Platinum-based chemotherapy, particularly carboplatin, is one of the main treatments used for ovarian cancer. When this treatment ceases to be effective, theoretically, olaparib might be less effective too, so the ICR scientists examined whether olaparib would still benefit patients whose response to previous platinum-based drugs was limited. Finding new drugs to treat these “platinum-resistant” ovarian cancer patients (those who relapsed within six months of previous platinum therapy) is a particularly high priority as they have a lower chance of benefiting from re-treatment with chemotherapy and a poorer prognosis.

The research team found that the clinical benefit rate with olaparib was indeed higher — 70% — among patients with “platinum-sensitive disease” (disease recurrence more than six months after previous platinum therapy). Crucially, however, the clinical benefit rate was still 46% in platinum resistant patients.

ICR Study Findings:

  • 50 patients participated in the study (13 had platinum-sensitive disease, 24 had platinum-resistant disease, and 13 had platinum-refractory disease (according to platinum-free interval).
  • 20 patients (40%) achieved complete or partial responses under RECIST (Response Evaluation Criteria in Solid Tumors) criteria and/or tumor marker (CA125) responses.
  • Overall clinical benefit rate (complete response + partial response + stable disease) = 46%.
  • Median response duration was 28 weeks.
  • There was a significant association between the clinical benefit rate and platinum-free interval across the platinum-sensitive, resistant, and refractory patient subgroups (69%, 45%, and 23%, respectively).
  • Analyses indicated associations between platinum sensitivity and extent of olaparib response.
  • CONCLUSION: Olaparib has antitumor activity in BRCA1/2 mutation ovarian cancer, which is associated with platinum sensitivity.

Up to 15 per cent of breast and ovarian cancers have known BRCA1 or BRCA2 mutations on blood testing and, importantly, laboratory data strongly suggests that olaparib may also be effective in cancers linked to DNA repair defects not caused by BRCA1 and BRCA2 mutations. This could apply in about half the cases of the most common histological type of ovarian cancer.

“We have good reason for thinking that the benefit seen with olaparib in BRCA mutation-linked ovarian cancer may well extend to a broader population of patients with this disease,” says Professor Kaye.

Randomised trials of olaparib – in which some patients receive the drug and others a placebo – are underway and results will be available later this year.

KuDOS Pharmaceuticals (a wholly owned subsidiary of AstraZeneca) was the major funder of the trial, along with Cancer Research UK and the National Institute for Health Research. Olaparib was identified and developed at KuDOS Pharmaceuticals and subsequently at AstraZeneca.

PARP Inhibitor Clinical Trials:

To view a list of open ovarian cancer clinical trials that are testing olaparib (AZD2281), click here.

To view a list of open solid tumor clinical trials that are testing olaparib (AZD2281), click here.

To view a list of open ovarian cancer clinical trials that are testing various PARP inhibitors, click here.

To view a list of open solid tumor clinical trials that are testing various PARP inhibitors, click here.

About The Institute of Cancer Research (ICR)

* The ICR is Europe’s leading cancer research centre.

* The ICR has been ranked the UK’s top academic research centre, based on the results of the Higher Education Funding Council’s Research Assessment Exercise.

* The ICR works closely with partner The Royal Marsden NHS Foundation Trust to ensure patients immediately benefit from new research. Together the two organisations form the largest comprehensive cancer centre in Europe.

* The ICR has charitable status and relies on voluntary income, spending 95 pence in every pound of total income directly on research.

* As a college of the University of London, the ICR also provides postgraduate higher education of international distinction.

* Over its 100-year history, the ICR’s achievements include identifying the potential link between smoking and lung cancer which was subsequently confirmed, discovering that DNA damage is the basic cause of cancer and isolating more cancer-related genes than any other organization in the world.

* The ICR is home to the world’s leading academic drug development team. Several important anti-cancer drugs used worldwide were synthesised at the ICR and it has discovered an average of two preclinical candidates each year over the past five years.

For more information visit www.icr.ac.uk.

About The Royal Marsden Hospital

The Royal Marsden opened its doors in 1851 as the world’s first hospital dedicated to cancer treatment, research and education. Today, together with its academic partner, The Institute of Cancer Research, it is the largest and most comprehensive cancer centre in Europe treating over 40,000 patients every year. It is a centre of excellence, and the only NHS Trust to achieve the highest possible ranking in the Healthcare Commission’s Annual Health Check for the third year in a row. Since 2004, the hospital’s charity, The Royal Marsden Cancer Campaign, has helped raise over £43 million to build theatres, diagnostic centres, and drug development units. Prince William became President of The Royal Marsden in 2007, following a long royal connection with the hospital.

For more information, visit www.royalmarsden.nhs.uk

About Cancer Research UK

* Cancer Research UK is the world’s leading charity dedicated to beating cancer through research.

* The charity’s groundbreaking work into the prevention, diagnosis and treatment of cancer has helped save millions of lives. This work is funded entirely by the public.

* Cancer Research UK has been at the heart of the progress that has already seen survival rates double in the last thirty years.

* Cancer Research UK supports research into all aspects of cancer through the work of more than 4,800 scientists, doctors and nurses.

* Together with its partners and supporters, Cancer Research UK’s vision is to beat cancer.

For further information about Cancer Research UK’s work or to find out how to support the charity, please call 020 7121 6699 or visit www.cancerresearchuk.org

About Experimental Cancer Medicine Centre (ECMC)

Experimental Cancer Medicine Centre (ECMC) status has been awarded to 19 centres in the UK that are specialist centres conducting research into new cancer treatments. The aim is to bring together cancer doctors, research nurses and lab scientists to make clinical trials of new treatments quicker and easier. The ECMC initiative is funded by Cancer Research UK and the Departments of Health of England, Scotland, Wales and Northern Ireland. Together they are giving a total of £35 million pounds over five years to the 19 centres. The centres will use this money to run trials of new and experimental treatments. They will also analyse thousands of blood and tissue samples (biopsies) to help find out more about how treatments work and what happens to cancer cells.

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