SM88 in non-metastatic rising PSA-recurrent prostate cancer.

Abstract

e16567 Background: SM88 is a novel combination of substituted amino acid ( AA) and repurposed agents with non-toxic activity in a variety of cancers including prostate (PC). Non-metastatic biochemically recurrent PC (nmPC) is ideal for such a well-tolerated, non-androgen based treatment. We present biomarker activity including CTCs (circulating tumor cells) after completion of the Ib dose escalating pharmacokinetic portion of the SM88 development plan. Methods: Planned analysis of an ongoing prospective Phase Ib/II open label study of nmPC (PCWG3 definition). Subject 1 received the 1stdose level of AA, and others received 2x dose. All subjects also received a combination of low dose re-purposed CYP3a4 inducer, oxidative stress catalyst, and mTOR inhibitor. Results: Four subjects completed at least 1 cycle (28d) with all PK sampling as prespecified. Median age was 73(70-80); all had prior ADT that was discontinued 3-6 yrs earlier, and either had curative intent prostatectomy (n = 2) or RT (n = 2); Testosterone level was castrate in one after prior RT. CTCs fell (p < 0.01) to undetectable (n = 1) or by > 25% (n = 3) (see table) while PSA remained stable (PCWG3 criteria). Preliminary LDH, neutrophil/lymphocyte ratio (N:L), urinary NTx, bone specific AlkPhos (bAP) trends are in the table below. There were no drug related serious adverse events (2 grade: 1- pigmentation, 1- vasomotor). EORTC-QLQ30 and PR25 scores were either improved or stable. Conclusions: Treatment with SM88 in patients with nmPC in the completed phase Ib cohort was associated with CTC reduction, and stable biomarker trends including PSA and LDH. There was no significant toxicity or adverse patient reported outcomes. Based on these results, the dose escalation was stopped at the second level and a cohort expansion phase II initiated. A phase III RCT is planned for confirmation of these results. Clinical trial information: NCT02796898. [Table: see text]