Phase 1, dose-escalation study of KTX-2001 (an NSD2 inhibitor) alone and in combination with darolutamide for metastatic castration-resistant prostate cancer.

TPS276 Background: Metastatic castration-resistant prostate cancer (mCRPC) can evolve into a neuroendocrine-like subtype with aggressive behavior and poor outcomes (1). Nuclear Receptor-Binding SET Domain Protein 2 (NSD2) is overexpressed in prostate cancer and is a driver of both androgen-receptor (AR)-dependent signaling and of neuroendocrine differentiation, where cancer cells lose AR dependence and response to AR pathway inhibitors (ARPIs) (2,3,4). In studies of patient-derived neuroendocrine prostate cancer (NEPC) models, genetic depletion of NSD2 led to restoration of AR expression, reversal of adeno-to-neuroendocrine differentiation, and re-sensitization to ARPI (4). We hypothesize that NSD2 inhibition can reverse resistance to ARPIs in patients with progressive mCRPC, including with neuroendocrine differentiation. KTX-2001 is an oral, potent and selective small molecule inhibitor of NSD2. It is the sponsor’s second NSD2 inhibitor to enter the clinic. The sponsor’s first in class NSD2 inhibitor, KTX-1001, was shown to be tolerable and have preliminary efficacy in patients with relapsed/refractory multiple myeloma (5). Methods: STRIKE-001 (NCT07103018) is a multicenter, open-label phase 1 dose escalation trial of KTX-2001 monotherapy (Part A) and KTX-2001 + darolutamide (Part B). Key inclusion criteria are males age ≥18 years with mCRPC, progression after receiving ARPI, Eastern Cooperative Oncology Group performance score of 0-1, willingness to undergo biopsy if safe and feasible, and life expectancy of ≥6 months. Participants take KTX-2001 by mouth once daily alone (Part A) or with darolutamide 600 mg twice daily (Part B). Dose escalation of KTX-2001 in Parts A and B will follow a 3+3 design and occur in parallel at multiple planned dose levels. Primary objectives are to assess the safety and tolerability, determine MTD, and determine RP2D(s) for further study of KTX-2001 alone and in combination with darolutamide. Secondary objectives include characterization of efficacy and PK parameters for both KTX-2001 monotherapy and in combination with darolutamide. Exploratory objectives include study of pharmacodynamic effects, circulating tumor cells, and cell-free DNA. 1. Conteduca V, Eur J Cancer 2019. 2. Parolia A, Nat Genet 2024. 3. Aytes A, Nat Commun 2018 4. Li J, bioRxiv 2023.07.18.549585 5. Bories P, Blood Vol 144, Suppl 1,2024. Clinical trial information: NCT07103018 .