Cabozantinib (XL184) demonstrated high rates of disease control in patients with prostate, ovarian and liver cancers. The investigators concluded that cabozantinib exhibits clinical activity in ovarian cancer patients with advanced disease, regardless of prior platinum drug status, as reflected by the high rates of response.
ASCO Releases Studies From Upcoming Annual Meeting – Important Advances in Targeted Therapies, Screening, and Personalized Medicine
The American Society of Clinical Oncology (ASCO) today highlighted several studies in a press briefing from among more than 4,000 abstracts publicly posted online at http://www.asco.org in advance of ASCO’s 47th Annual Meeting. An additional 17 plenary, late-breaking and other major studies will be released in on-site press conferences at the Annual Meeting.
The meeting, which is expected to draw approximately 30,000 cancer specialists, will be held June 3-7, 2011, at McCormick Place in Chicago, Illinois. The theme of this year’s meeting is “Patients. Pathways. Progress.”
“This year marks the 40th anniversary of the signing of the National Cancer Act, a law that led to major new investments in cancer research. Every day in our offices, and every year at the ASCO meeting, we see the results of those investments. People with cancer are living longer, with a better quality of life, than ever before,” said George W. Sledge Jr., M.D., President of ASCO, Ballve-Lantero Professor of Oncology and professor of pathology and laboratory medicine at the Indiana University School of Medicine.
“With our growing understanding of the nature of cancer development and behavior, cancer is becoming a chronic disease that a growing number of patients can live with for many years,” said Dr. Sledge. “The studies released today are the latest examples of progress against the disease, from new personalized treatments, to new approaches to screening and prevention.”
The study results from a phase II clinical trial involving cabozantinib (XL184) were highlighted today in the ASCO press briefing, as summarized below.
Novel Multi-targeted Agent Cabozantinib (XL184) Has Significant Effect on Several Advanced Solid Tumors, and Can Shrink or Eliminate Bone Metastases
Cabozantinib (XL184) – an oral inhibitor of MET and VEGFR2 kinases involved in the development and progression of many cancers – showed strong responses in patients with various advanced cancers in a phase II trial. The drug demonstrated particularly high rates of disease control for advanced prostate, ovarian and liver cancers, which are historically resistant to available therapies. The drug also fully or partially eliminated bone metastases in patients with breast and prostate cancers and melanoma.
“Cabozantinib appears to have significant effects on several treatment-resistant tumors, as well as impressive effects on bone metastases. In addition, these effects are associated with rapid improvement in pain, a reduction in opiate narcotic requirements and improvement in anemia,” said lead author Michael S. Gordon, M.D., a medical oncologist at Pinnacle Oncology Hematology located in Scottsdale, Arizona. “The implications of these results are very exciting—it is unusual to find a targeted therapy, absent of a molecular mutation in tumors, that works in bony disease and has this activity.”
To be eligible for the study, patients had to have advanced, progressive solid tumors, with or without bone metastases. Of 398 evaluable patients (of 483 enrolled in the trial), 39 percent had bone metastases at baseline. Patients received cabozantinib over 12 weeks. The trial was designed as a “discontinuation” trial, in which those who had partial responses stayed on the drug; those with stable disease were randomized to cabozantinib or placebo; and patients with progressive disease were removed from the trial. This novel type of clinical trial design more quickly evaluates the disease-stabilizing activity of growth-inhibitory agents like cabozantinib, compared to the traditional model of randomizing all patients to either the experimental arm or placebo.
Among 398 patients evaluable with all types of cancer included in the trial, the collective overall response rate was 9 percent (34 of 398). The highest disease control rates (partial response and stable disease) at week 12 were 76 percent for liver cancer (22 of 29 patients), 71 percent for prostate cancer (71 of 100 patients), and 58 percent for ovarian cancer (32 of 51 patients). [emphasis added].
Of the 51 evaluable ovarian cancer patients noted above, 28 are platinum drug resistant, 17 are platinum drug sensitive, and 6 have unknown status. The median number of systemic treatments prior to trial enrollment was 2. The overall response rate (complete response and partial response based on modified RECIST criteria) for ovarian cancer was 12/51 (24%). Upon breakdown, the response rate was 5/28 (18%) for platinum drug resistant patients, and 5/17 (29%) for platinum drug sensitive patients. Five additional partial responses await confirmation. After a median follow-up of 4 months (range: 1 to 11 months), the median duration of response and median progression free survival have not been reached. The most common related adverse events ( ≥grade 3) among ovarian cancer patients were hand-foot syndrome (10%), diarrhea (8%) and fatigue (4%). Drug dose reductions and permanent discontinuations for adverse events occurred in 43% and 10% of the ovarian cancer patients, respectively. Based on these findings, the investigators concluded that cabozantinib exhibits clinical activity in ovarian cancer patients with advanced disease, regardless of prior platinum drug status, as reflected by the high rates of response. [emphasis added] Accordingly, randomization in the ovarian cancer cohort was halted & patients unblinded due to the observed high efficacy.
Fifty-nine of 68 patients with bone metastases (including patients with breast and prostate cancers and melanoma) experienced either partial or complete disappearance of the cancer on bone scans, often with significant pain relief and other improved cancer-related symptoms.
The reduction of bone metastases and pain relief was an unexpected finding in this study, Dr. Gordon said. Independent review by radiologists confirmed that bone metastases disappeared in the majority of patients who had bone metastases when they entered the study. The majority of these patients had castration-resistant prostate cancer (CRPC), but patients with breast cancer and melanoma also had disappearance of bone metastases. Bone metastases greatly contribute to morbidity and mortality in patients with these types of cancer, which typically spread to the bone.
Due to these results, the study has been expanded to include more CRPC patients. Similarly, the high rate of lasting responses in ovarian cancer patients led researchers to also expand the study to evaluate the drug’s effect on patients with a particularly resistant form of the disease known as platinum drug resistant/refractory ovarian cancer. [emphasis added]
This study expansion results will help determine the design of future phase III trials, which will assess whether the drug extends patients lives or has other longer-term benefits among patients with specific cancer types. At present, cabozantinib is being investigated for use as a single agent. Additional studies will evaluate the efficacy and tolerability of appropriate combinations with other agents for future indications.
For the solid tumor patients collectively, the most common grade three or above adverse events were fatigue (9 percent) and hand-foot syndrome (8 percent). Dose reductions were required in 41 percent of patients due to side effects; 12 percent were removed from the trial for adverse events.
- ASCO Releases Studies From Upcoming Annual Meeting – Important Advances in Targeted Therapies, Screening, and Personalized Medicine – Novel Multi-targeted Agent Cabozantinib (XL184) Has Significant Effect on Several Advanced Solid Tumors, and Can Shrink or Eliminate Bone Metastases , Press Release, American Society of Clinical Oncology, May 18, 2011. [Adobe Reader PDF]
- Gordon MS, Vogelzang NJ, Schoffski P, et. al. Activity of cabozantinib (XL184) in soft tissue and bone: Results of a phase II randomized discontinuation trial (RDT) in patients (pts) with advanced solid tumors. J Clin Oncol 29: 2011 (suppl; abstr 3010)(2011 ASCO Annual Meeting).
- Buckanovich R.J., Berger R, Sella A, et. al. Activity of cabozantinib (XL184) in advanced ovarian cancer patients (pts): Results from a phase II randomized discontinuation trial (RDT). J Clin Oncol 29: 2011 (suppl; abstr 5008)(2011 ASCO Annual Meeting).
- Hussain M, Smith MR, Sweeney C., et. al. Cabozantinib (XL184) in metastatic castration-resistant prostate cancer (mCRPC): Results from a phase II randomized discontinuation trial. J Clin Oncol 29: 2011 (suppl; abstr 4516)(2011 ASCO Annual Meeting).
- Cabozantinib Helps Manage Several Advanced Cancers and Shrink Bone Metastases, http://www.Cancer.net, May 18, 2011.
- A list of open solid tumor clinical trials involving cabozantinib (XL184).
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