Rapid and Durable Responses with the SYK/JAK Inhibitor Cerdulatinib in a Phase 2 Study in Relapsed/Refractory Follicular Lymphoma-Alone or in Combination with Rituximab

Background: Despite recent advances, follicular lymphoma (FL) remains incurable for most patients. Relapsed/refractory (r/r) FL is associated with decremental treatment responses, accumulating toxicity, and poor survival among early failures of 1st line chemoimmunotherapy. Underscored by the recent approvals of idelalisib, copanlisib, and duvelisib, targeting B-cell receptor (BCR) signaling produces ORR of ~50% in r/r patients; however, new agents with a better therapeutic index over long-term administration are needed.

SYK is a key regulator of BCR signaling (upstream of BTK and PI3K), and its inhibition results in clinical activity in FL. Compared with unaffected nodes, lymph nodes from FL patients have greater numbers of follicular helper T cells that express high levels of IL-4, which may support the tumor via the JAK1/3 pathway.

Cerdulatinib, an oral, reversible inhibitor of SYK and JAK kinases (JAK1, JAK3, TYK2), previously reported a ~45% overall response rate (ORR) in r/r FL as a single agent. Xenograft studies suggest cerdulatinib may combine with rituximab to enhance antitumor activity. We report updated results from a phase 2a study of single-agent cerdulatinib and initial results in combination with rituximab in r/r FL.

Methods: This phase 2a study confirmed the safety and efficacy of cerdulatinib 30 mg BID in r/r B- and T-cell lymphoma patients. Dose reductions were permitted to 15 mg BID. Response was assessed by Lugano criteria.

Results: A planned interim analysis was performed on July 18, 2019, in which enrollment was 40 patients in the single-agent cohort and 19 patients in the rituximab combination cohort. For the single-agent cohort, median age (range) was 64 (42-81) years and median prior therapies (range) was 3 (1-9). Ninety-five percent of patients had prior anti-CD20 therapy, and 25% had prior therapy with BCR pathway inhibitors. For the combination cohort, median age (range) was 67 (47-85) years and median prior therapies (range) was 3 (1-10). Eighty-eight percent of patients had prior anti-CD20 therapy, and 32% had prior therapy with BCR pathway inhibitors. The safety profile appeared similar in both cohorts. The most common treatment-emergent grade 3+ adverse events in ≥5% of patients for both cohorts were lipase increase (27%), neutropenia (18%), diarrhea (12%), amylase increase (10%), hypertension (8%), nausea (7%), and pneumonia (5%). Grade 3+ infections occurred in 17.5% of single-agent cohort patients and 15.8% of combination cohort patients. Amylase and lipase increases generally were not associated with abdominal pain or pancreatitis. In addition, to date there has been no evidence of cumulative toxicity.

The ORR was 45% as a single agent (12.5% complete response [CR], 32.5% partial response [PR], with 25% stable disease [SD] and 5% progressive disease [PD] in 40 evaluable patients) and 59% in the combination cohort (11.7% CR, 47% PR, with 27.8% SD and no PD in 17 evaluable patients). Responses typically occurred after 2 cycles, generally improved over time, and were durable in the single-agent cohort, with 10 patients on drug for >1 year. Enrollment in the combination cohort is ongoing. Updated safety and efficacy will be presented.

Conclusion: The recommended cerdulatinib phase 2 dose of 30 mg BID was tolerable and efficacious in heavily pretreated r/r FL. The cerdulatinib + rituximab combination appears to be well tolerated, with tumor reductions in all evaluable patients. The safety profile and unique mechanism of action of cerdulatinib support further combination studies in FL.