PK and Dose Escalation and Expansion Study of DST-2970

This is a Phase I multi-center, open-label, study of DST-2970 to determine the MTD, overall safety/tolerability, PK/pharmacodynamic parameters, and efficacy in prostate cancer patients.The study will include a dose escalation phase followed by a dose expansion phase. Each cohort will consist of a "run-in" period to assess pharmacokinetic trough, as well as C1hour, C2hour, and C3hour levels of standard of care abiraterone acetate, followed by a minimum of an 80-hour washout (treatment delay), then initiation of treatment with DST-2970. The patient population that will be evaluated in this study include patients with castration sensitive or castration resistant prostate cancer who experience a rising PSA, with or without radiographic progression, while taking abiraterone acetate. In this protocol, "initial PSA response to abiraterone" is defined as having a ≥ 30% drop in PSA levels (confirmed by a second PSA level one month later) during the first 6 months of treatment with abiraterone. These patients who subsequently experience a rise in PSA while on abiraterone are considered as having "acquired resistance" to abiraterone in the context of this protocol. Patients not meeting the definition of having an "initial PSA response to abiraterone" are considered as having "primary resistance" to abiraterone in the context of the protocol. In the dose escalation phase, all patients with a rising PSA can be enrolled, whether they had an "initial PSA response to abiraterone" or never responded to abiraterone. Two expansion cohorts will be opened. One expansion cohort will evaluate patients who did achieve an "initial PSA response to abiraterone" within the first 6 months of treatment as defined above, but subsequently progressed by PSA with or without radiographic progression. A second expansion cohort will evaluate patients who did not achieve an "initial PSA response to abiraterone" as defined above but have PSA progression with or without radiographic progression. The rationale of the study is to determine if the better bioavailability of DST-2970 will overcome resistance to abiraterone acetate experienced in these two clinical settings. In all cohorts, treatment will continue until progressive disease, unacceptable toxicity, investigator and/or sponsor decision, intercurrent illness or patient withdrawal of consent. Patients will be monitored regularly with physical examination and laboratory tests.