Parsaclisib, a potent and highly selective PI3Kδ inhibitor, in patients with relapsed or refractory B-cell malignancies

Andres Forero-Torres, Radhakrishnan Ramchandren, Abdulraheem Yacoub, Michael S. Wertheim, William J. Edenfield, Paolo Caimi, Martin Gutierrez, Luke Akard, Carolina Escobar, Justin Call, Daniel Persky, Swaminathan Iyer, Douglas J. DeMarini, Li Zhou, Xuejun Chen, Fitzroy Dawkins and Tycel J. Phillips

Key points

  • Parsaclisib is a potent, highly selective, next-generation PI3Kδ inhibitor that is not associated with clinically meaningful transaminitis.

  • The objective response rates and encouraging long-term tolerability observed in this study warrant further investigation in NHL subtypes.


This phase 1/2 study assessed parsaclisib (INCB050465), a next-generation, potent, and highly selective phosphatidylinositol 3-kinase δ (PI3Kδ) inhibitor, in patients with relapsed or refractory B-cell malignancies, alone or in combination with a Janus kinase 1 inhibitor (itacitinib) or chemotherapy (rituximab, ifosfamide, carboplatin, and etoposide). Seventy-two patients received parsaclisib monotherapy (5-45 mg once daily). Expansion doses were 20 and 30 mg once daily; intermittent dosing at 20 mg (once daily for 9 weeks, then once weekly) was explored. No dose-limiting toxicities were identified, and maximum tolerated dose was not reached. Most common nonhematologic treatment-emergent adverse events (TEAEs) were diarrhea/colitis (36%), nausea (36%), fatigue (31%), and rash (31%). Grade 3/4 neutropenia occurred in 19% of patients. Serious TEAEs (> 2 patients) were diarrhea/colitis (n = 9), pyrexia (n = 4), hypotension (n = 3), and sepsis (n = 3). Aspartate and alanine transaminase elevations occurring before treatment discontinuation were grade 1, except 1 grade 3 event each, secondary to sepsis. Two patients experienced 3 fatal parsaclisib-unrelated TEAEs (respiratory failure; respiratory failure and sepsis). In non-Hodgkin lymphoma (NHL), objective response rates to monotherapy were 71% in follicular lymphoma, 78% in marginal zone lymphoma, 67% in mantle cell lymphoma, and 30% in diffuse large B-cell lymphoma; 93% of responses occurred at first assessment (~9 weeks). Parsaclisib has demonstrated antitumor activity in relapsed or refractory B-cell NHL with the potential for improved long-term patient outcomes. Phase 2 studies in relapsed or refractory B-cell NHL subtypes are ongoing. This trial was registered at as #NCT02018861.

  • Submitted August 22, 2018.
  • Accepted February 5, 2019.