Feasibility of Combining the Phosphatidylinositol 3-Kinase Inhibitor Copanlisib With Rituximab-Based Immunochemotherapy in Patients With Relapsed Indolent B-cell Lymphoma

Background: When treating indolent B-cell lymphoma, combining continuously administered oral phosphatidylinositol 3-kinase (PI3K) inhibitors with immunochemotherapy has been associated with toxicity. CHRONOS-4 (Phase III; NCT02626455) investigates the intravenous, intermittently administered pan-class I PI3K inhibitor copanlisib in combination with rituximab plus bendamustine (R-B) or rituximab plus cyclophosphamide, doxorubicin, vincristine, and prednisone (R-CHOP) in patients with relapsed indolent B-cell lymphoma. We report safety run-in results. Patients and Methods: Patients aged ≥18 years with relapsed CD20-positive indolent B-cell lymphoma received copanlisib (45 mg, increasing to 60 mg if no dose-limiting toxicities) weekly on an intermittent schedule with R-B or R-CHOP. Primary objective was to identify a recommended Phase III dose (RP3D). We also assessed objective response, safety, and tolerability. Results: Ten patients received copanlisib plus R-B and 11 received copanlisib plus R-CHOP. No dose-limiting toxicities were reported; RP3D was 60 mg. All patients had ≥1 treatment-emergent adverse event (TEAE), most commonly (all grade/grade 3/4) for copanlisib plus R-B: decreased neutrophil count (80%/50%), nausea (70%/0%), decreased platelet count (60%/10%), hyperglycemia (60%/50%); for copanlisib plus R-CHOP: hyperglycemia (82%/64%), hypertension (73%/64%), decreased neutrophil count (64%/64%). Two and 8 patients had serious TEAEs with copanlisib plus R-B and R-CHOP, respectively. Among evaluable patients, objective response rates were 90% (5 complete, 4 partial) and 100% (3 complete, 7 partial) with copanlisib plus R-B and R-CHOP, respectively. Conclusion: Copanlisib is the first PI3K inhibitor to demonstrate safe, tolerable, and effective combinability with immunochemotherapy in patients with relapsed indolent B-cell lymphoma at full dose (60 mg). Further evaluation is ongoing.