Tazemetostat in combination with topotecan and pembrolizumab in patients with recurrent small cell lung cancer.

TPS8130 Background: Small-cell lung cancer (SCLC) is the most fatal type of lung cancer characterized by exquisite chemo-sensitivity at diagnosis and chemoresistance at relapse. Despite a highly mutated genome, patients with SCLC derive little benefit from immunotherapy. EZH2 (enhancer of zeste homolog 2) is a master epigenetic regulator of SCLC neuroendocrine cell fate and plasticity. EZH2 inhibition 1) promotes upregulation of Schlafen 11 (SLFN11) which irreversibly blocks replication in response to DNA damaging agents and 2) enhances intrinsic immune signaling, leading to constitutive MHC I recovery, sensitizing resistant SCLC models to DNA damaging chemotherapy and immunotherapy. Tazemetostat is a selective oral EZH2 inhibitor. Methods: This is an investigator-initiated, NCI Cancer Therapy Evaluation Program (CTEP) sponsored, phase I dose escalation and dose expansion study which will evaluate safety and tolerability of combination of tazemetostat with topotecan, a selective TOP1 inhibitor, and programmed cell death protein 1 (PD-1) inhibitor antibody pembrolizumab. Adult patients with relapsed/recurrent SCLC after at least platinum doublet (limited stage-SCLC) or chemo-immunotherapy (extensive stage-SCLC) and ECOG performance 0-1 are eligible. The regimen design involves a 7-day “run-in” of oral tazemetostat BID followed by 21-day cycles of tazemetostat (1-21 days), intravenous (IV) topotecan (day 1-5) and IV pembrolizumab (Day 1). The dose escalation cohort aims to determine safety and optimal doses of tazemetostat and topotecan (with standard dose of pembrolizumab) using a 3+3 design by assessing for dose limiting toxicities. The dose expansion cohort aims to assess safety, tolerability and preliminary efficacy of the combination in 15 additional patients with relapsed SCLC. The study involves collection of mandatory biopsies at pre-treatment and post-treatment (cycle 1) to gain insights into mechanism of action and resistance of the combination using single cell and spatial transcriptomic approaches. For more questions regarding enrollment and eligibility please contact Rasa.vilimas@nih.gov or anish.thomas@nih.gov . Clinical trial information: NCT05353439 .