Novel ACK1 Inhibitor (R)-9b in Patients With Prostate Cancer

TITLE: Phase 1 First in Human Trial to Assess Safety and Tolerability of the Novel ACK1 Inhibitor (R)-9bMS in Patients with Prostate Cancer (PHAROS) STUDY DESCRIPTION: Prostate cancer (PC) patients receive androgen deprivation therapy (ADT), but recalcitrant disease recurs typically within 2-3 years, referred to as the Castration Resistant Prostate Cancer (CRPC). Androgen receptor (AR) targeted therapies, such as Enzalutamide (Enz) or Abiraterone (Abi), are FDA-approved therapeutics for CRPC patients. However, virtually all patients develop resistance. A non-receptor tyrosine kinase, ACK1 act as a novel epigenetic modifier in prostate tumors, regulating AR and its splice variant, AR-V7 expression. A new class of ACK1 small molecule inhibitor, (R)-9bMS, was developed that exhibited excellent drug-like properties. Treatment with (R)-9bMS suppressed Abi and Enz-resistant tumor growth in mice. Robust immune activation against prostate tumors was also reflected in mice treated with ACK1 inhibitor, (R)-9bMS. Importantly (R)-9bMS functionally reinvigorated peripheral blood mononuclear cells (PBMCs) of CRPC patients to mount a robust immune response against CRPC organoids. Collectively, these data indicate that the ACK1 inhibitor, (R)-9bMS, fulfills a unique niche, wherein it not only suppressed AR/AR-V7 within the tumor milieu, but also activated host immune system by overcoming CSK-restrained LCK activity, to mount a robust 'dual' anti-tumor response. OBJECTIVES: Primary Objective: To assess the safety and tolerability of (R)-9bMS in patients with metastatic castration-resistant prostate cancer. Secondary Objectives: To determine the maximum tolerated dose (MTD) and recommended phase 2 dose (RP2D) of (R)-9bMS in patients with CRPC. To determine the pharmacokinetics (PK) of (R)-9bMS in patients after single and multiple dose oral administration. To assess clinical outcomes and anti-tumor activity in patients treated with (R)-9bMS. ENDPOINTS: Primary Endpoint: Frequency of dose-limiting toxicities and toxicity and severe AEs per CTCAE v 5.0. Secondary Endpoints:

• RP2D (recommended phase 2 dose)
• PK (pharmacokinetics)
• PSA responses
• Duration of responses
• ORR (objective response rate)
• OS (overall survival)
• PFS (progression free survival)
• DSS (disease specific survival)
• Toxicity and severe AEs per CTCAE v 5.0 STUDY POPULATION: Approximately 18-30 adult patients with a histologic or cytologic diagnosis of metastatic castration resistant prostate cancer will be enrolled. PHASE: Phase I DESCRIPTION OF SITES: This study will be open to enrollment at the University of Wisconsin Carbone Cancer Center DESCRIPTION OF STUDY INERVENTION: (R)-9bMS will be taken by mouth twice daily until completion of 12 cycles, progression or intolerance STUDY DURATION: 12 months for enrollment + 12 months treatment + 12 months follow-up + 12 months for data analysis = 48 months.