The following article features coverage from the American Society of Hematology 2019 meeting. Click here to read more of Cancer Therapy Advisor‘s conference coverage.

The combination of idelalisib plus obinutuzumab resulted in a 69% overall response rate in patients with relapsed or refractory Waldenström macroglobulinemia (WM), according to results presented at the 61st American Society of Hematology (ASH) Annual Meeting and Exposition in Orlando, Florida.

The phase 2 study included 49 patients with relapsed or refractory WM assigned to induction 150 mg idelalisib twice daily with obinutuzumab. During a maintenance phase, 28 patients continued on idelalisib alone for a maximum duration of 2 years.

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With a median follow-up of 17 months, 34 patients had responded. The overall response rate was 69%. Although no patients achieved a complete response, 6% achieved a very good partial response, and 53% achieved a partial response.

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The median progression-free survival was longer than 2 years (25 months). Seventy-seven percent of patients had no progression at the end of 1 year, and 57% had no progression at the end of 2 years. The one-year overall survival was 98%, and the 2- year overall survival was 88%.

The majority of grade 3 or worse adverse events or serious adverse events were hepatotoxicity, diarrhea, and neutropenia, which are known side effects of idelalisib.

Most of the patients (45 of 49, or 92%) experienced at least one grade 3 or worse adverse event.

Although the investigators reported that there were no unexpected toxicities associated with the combination of obinutuzumab and idelalisib, dose reductions occurred in 43% of the patients; idelalisib, specifically, had a discontinuation rate of 49%.

Disclosure: Some of the authors disclosed financial relationships with the pharmaceutical industry. For a full list of disclosures, please refer to the original abstract.

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Tomowiak C, Desseaux K, Poulain S, et al. Open label non-randomized phase II study exploring <<chemo-free>> treatment association with idelalisib + obinutuzumab in patients with relapsed/refractory (R/R) Waldenstrom’s macroglobulinemia (MW), a Filo trial: Results of the intermediary analysis of the induction phase. Presented at: 61st American Society of Hematology (ASH) Annual Meeting and Exposition; December 7-10, 2019; Orlando, FL. Abstract 346.