Evaluating non-hormonal therapy in a phase II trial of SM-88 for rising PSA prostate cancer.

Abstract

83 Background: Absolute PSA change is an imperfect surrogate of clinical benefit; CTCs and PSA doubling time (DT) may also be used as a surrogate of progression (PD). Hormone therapy (HT) often leads to a rapid decline in PSA, however non-HT may be effective without causing a decline in absolute PSA or testosterone (T). SM-88, a non-HT novel combination Warburg effect therapy (amino acid analogue, CYP3a4 inducer, mTOR inhibitor and catalyst) does not affect T. We report outcomes leading to subsequent therapies of an ongoing PSA recurrent, non-metastatic PC trial. Methods: Prospective Phase II of rising PSA (per PCWG3), detectable CTCs, and no baseline lesions. Results: Since September 2016, 31 subjects enrolled with 17 on study for > 12 weeks. Mean age 68.9; BMI 28.7; 38% black and 62% post RT. Mean T increased 61 mg/dl from baseline 319 mg/dl (p=0.19). 82% (14/17) subjects experienced an improvement in PSA DT and 67% (10/15) experienced a decline in CTCs of >30%. Overall median PSA DT time on enrollment was 5.3 (1.4 – 37.6) and improved to 6.5 (Wilcoxon p=0.02) (see table). 3/4 subjects with PD failed to maintain a CTC drop >60% vs 2/17 without PD (p=.03); median time to nadir CTC was 3 cycles (1-7). Subjects avoiding subsequent therapy averaged a 50% CTC decline (15-100%). CTC and PSA DT effects were not correlated to T level. AEs possibly related to drug/unrelated were: No grade (G) 4 or 5; 0/1 G3; 1/7 G2; 13/19 G1. As reported elsewhere, typical HT-related side effects were not observed. Including all patients with >1 month of data, from initial diagnosis of PSA rise (median 9 months; 3-18), 96% (22/23) have remained metastases-free and 78% (18/23) remained free of additional HT (p<.05). Clinical trial information: NCT02796898. Conclusions: SM-88 may be a useful either before or as an additive to current PC treatments where normal T may be preferred. SM-88 might not worsen QOL parameters related to T level. An effect on PSA DT and CTCs were demonstrated even in an aggressive doubling time subgroup. Prospective trials are planned to confirm its utility.[Table: see text]