What we already know: Exelixis is expected to file for the approval of cabozantinib ("cabo") for the treatment of advanced medullary thyroid cancer later this quarter. More importantly, the company is enrolling prostate cancer patients in two phase III studies of cabozantinib.

What's new in the ASCO abstracts: Abstract No. 5508 reports on results from the phase III study of cabo in medullary thyroid cancer. A 7.2-month benefit in progression-free survival (11.2 months for cabo vs. 4 months for placebo) was previously reported. New data includes response rate (28% for cabo vs. 0% for placebo) and an interim analysis of overall survival yielding no difference between cabo and placebo. The survival analysis was conducted on 44% of planned deaths in the study.

A non-randomized expansion of a previously reported phase II study enrolled 93 patients with advanced prostate cancer patients that had spread to bone, causing pain requiring treatment with painkillers. The patients were treated with 100 mg daily of cabozantinib. Abstract No. 4513 describes interim results: 51 of 85 patients (60%) achieved a partial bone scan response, while 21 of 30 patients (70%) had reduction of measurable disease. The abstract doesn't specify how many patients achieved a true complete or partial tumor response.

Forty-six percent (16 of 33 patients) reported a durable reduction in pain and decreased narcotics use. Of these patients, 27% discontinued narcotics. In 59 patients with measurable circulating cancer cells, 92% had a decrease of 30% or greater and 39% had circulating tumor cell reductions below the level of detection.


What we already know: Pharmacyclics and partner Johnson & Johnson are starting pivotal studies of ibrutinib in patients with relapsed or refractory chronic lymphocytic leukemia (CLL). Last December, the companies presented data from a phase II study of ibrutinib in elderly patients with relapsed/refractory CLL showing response rates of 67-68%.

What's new in the ASCO abstracts: From the same study, an interim analysis from a group of treatment-naive, elderly CLL patients treated with ibrutinib showed an overall response rate of 73%, including 8% complete responses and 65% partial responses. The estimated one-year progression-free survival is 93%. (Abstract No. 6507.)

Abstract No. 6508 reports on interim results from a phase Ib/II study combining ibrutinib with Glaxo's Arzerra in patients with relapsed/refractory CLL. The overall response rate to the combination therapy was 100%, all partial responses.

Ariad Pharmaceuticals

What we already know: Interim results from the ponatinib "PACE" study in chronic myelogenous leukemia were first presented last December. With a median reported 5.6-month follow up, 47% of patients reported a major cytogenic, or cellular, response. In the subgroup of CML patients with the T315I mutation, the major cytogenic response was 65%.

What's new in the ASCO abstract: The response data are little changed from the December update because the ASCO abstract (No. 6053) was submitted in January, reflecting a median 6.6 months of follow up. The overall major cytogenic response for CML patients is 49% (higher than in December.) In the T315I subgroup, the response rate is 62% (lower than in December.)

A significant update of results from the PACE study will be presented at ASCO, with six-month follow-up data on all patients available.


What we know already: Top-line data from a phase II study of tivantinib in second-line liver cancer were released in January. Liver cancer patients who progressed after first-line therapy were randomized 2:1 to receive tivantinib or a placebo. The study met its primary endpoint with tivantinib demonstrating a 56% improvement in time to tumor regrowth (time to progression, or TTP) compared to the placebo.

What's new in the ASCO abstract: In the overall patient population, tivantinib-treated patients reported a median time to progression of 1.6 months compared to 1.4 months for placebo patients. The small difference was statistically significant with a p value of 0.04. (Abstract No. 6503)

In a subset of patients who over-expressed c-Met, the molecular target of tivantinib, median TTP was 2.9 months for drug versus 1.5 months for placebo -- a statistically significant benefit. In this same patient subgroup, progression-free survival was 2.4 months for tivantinib compared to 1.5 months for placebo -- statistically significant.

A preliminary overall survival analysis trends in tivantinib's favor but is not yet statistically significant. Placebo patients were allowed to cross over and receive tivantinib when their tumors started to grow again.

Tivantinib dose was reduced mid-study due to reports of low blood cell counts in some patients. This helped reduce the rate of neutropenia from 21% to 6%. The most frequent drug-related serious adverse event was neutropenic sepsis (4.2%).

Other notes: Arqule and partner Daiichi Sankyo are conducting a phase III study of tivantinib in non-small cell lung cancer, with an interim analysis expected in the fourth quarter. A phase II study of tivantinib in colon cancer is also ongoing with results possible by year-end or in early 2013.


What we know already: Phase I trials showed the experimental drug PX-866 to be well tolerated with some evidence of anti-cancer activity. Oncothyreon is conducting phase II studies of PX-866 in combination with other drugs in non-small cell lung cancer, glioblastoma, prostate cancer, colon cancer and head-and-neck cancer.

What's new in the ASCO abstracts: Interim results from the PX-866 study in patients with recurrent glioblastoma (brain tumors) are described in Abstract No. 2051. Seventeen patients were enrolled and treated with PX-866, 14 of which are evaluable for response. Twelve patients discontinued the study -- nine due to progressive disease and three due to serious elevations of liver enzymes indicative of liver damage.

--Written by Adam Feuerstein in Boston.

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Adam Feuerstein writes regularly for TheStreet. In keeping with company editorial policy, he doesn't own or short individual stocks, although he owns stock in TheStreet. He also doesn't invest in hedge funds or other private investment partnerships. Feuerstein appreciates your feedback; click here to send him an email.

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