(Reuters) - Patients with a type of leukemia that had relapsed who received the new drug Venclexta in combination with Rituxan went significantly longer without the disease worsening than those treated with Rituxan and Treanda, according to interim results from a pivotal late stage study released on Tuesday.
Venclexta, sold by Roche and AbbVie, received an accelerated approval to treat chronic lymphocytic leukemia (CLL) patients with a specific genetic mutation who received at least one prior therapy.
But its continued approval, which was based only on overall response rates seen in an earlier trial, may be contingent on confirmation of clinical benefit.
The Phase III interim data being presented next month at the American Society of Hematology (ASH) meeting in Atlanta may go a long way to providing that confirmation.
In the study of 389 patients whose CLL had relapsed after up to three prior treatment regimens, median time until disease worsening, or progression-free survival (PFS), was 17 months for Rituxan plus Treanda, know generically as bendamustine. Median PFS was not yet reached after two years of treatment with the Venclexta combination, including in high-risk patients.
“The primary analysis of the first Phase III study of Venclexta in relapsed/refractory CLL shows a profound improvement in PFS versus standard bendamustine/Rituxan, with consistent effects in all-risk subsets,” researchers concluded in a brief summary of interim data released on Tuesday.
The overall response rate was 93.3 percent for Venclexta plus Rituxan versus 67.7 percent who responded to Treanda/Rituxan.
A complete response, meaning no detectable sign of cancer based on bone marrow assessment and CT scan, was observed in 26.8 percent of those who received Venclexta (venetoclax) plus Rituxan versus 8.2 percent of those in the control group.
The results were deemed to be highly statistically significant.
Adverse reactions leading to deaths were reported in 10 Venclexta patients (5.2 percent) and 11 in the Treanda group (5.9 percent).
CLL is a slowly progressing blood cancer that primarily affects older adults. About 20,000 new cases of CLL are diagnosed in the United States each year, according to the American Cancer Society.
Treanda is sold by Teva Pharmaceutical Industries and Rituxan (rituximab) is sold by Roche and Biogen.
Reporting by Bill Berkrot; Editing by James Dalgleish