An interim analysis from the Phase 2/3 clinical trial assessing Mateon Therapeutics‘ CA4P suggests the drug therapy is safe and effective in platinum-resistant ovarian cancer patients, when used in combination with physician’s choice chemotherapy and Avastin (bevacizumab).

“I am encouraged that the safety data is better than we expected and that the efficacy data is in line with our expectations,” William D. Schwieterman, MD, Mateon’s president and CEO, said in a press release. “After executing on the strategy we developed in late 2015, it is gratifying to be able to report new data for CA4P supporting its use in combination with bevacizumab and chemotherapy as a new treatment for platinum-resistant ovarian cancer. I am eager to see results from the additional interim analyses planned for later this year,” he said.

Mateon’s CA4P (Combretastatin A4 phosphate) is a novel vascular disrupting agent that induces acute reductions in tumor blood flow. Used alone, CA4P has been shown to induce extensive cell death in a variety of cancer mouse models, and decrease blood flow in patient tumors.

But pre-clinical and clinical data suggest that CA4P may be more effective when combined with radiotherapy or chemotherapy and with anti-angiogenic therapies, like Avastin, which prevent the formation of new blood vessels.

The FOCUS Phase 2/3 trial (NCT02641639) is a randomized, double-blind, two-arm, parallel-group trial, designed to evaluate the safety and effectiveness of CA4P combined with physician’s choice chemotherapy (PCC) and Avastin, versus PCC and Avastin alone, in ovarian cancer patients who progressed within six months of receiving their last platinum-based chemotherapy. Eligible patients had received at least one, but no more than two, prior platinum-based regimens.

Results from the interim analysis, which was conducted after the first 20 enrolled patients received two months of therapy or discontinued from the trial, have demonstrated that CA4P’s safety profile was similar or better to that seen in prior CA4P trials.

The most common adverse event was acute increase in blood pressure, which was observed in 89% of CA4P-treated patients, versus in 20% of patients in the control arm. Other side effects included anemia, abdominal pain, nausea, constipation, fatigue, shortness of breath, cough and vomiting, but they all were  mild to moderate.

The company also reported lower-than-expected rates of blood-related adverse events, with no patients experiencing low blood counts of neutrophils or white blood cells.

While it is too early in the trial to draw conclusions regarding the combo’s effectiveness, the recent analysis shows a better progression-free survival rate in CA4P-treated patients. Similarly, the proportion of patients who responded to treatment also was higher in the CA4P arm. Two out of nine CA4P-treated patients had a partial response, with a 76% and 64% reduction in their tumors, respectively, while only one out of 11 patients in the control arm responded, with a 46% reduction in his tumor.