Figure 6: CCS1477 decreases AR and AR-V7 signaling and inhibits growth in a patient- derived model of lethal prostate cancer.

(a) Patient-derived xenograft (PDX) CP50c was developed from lymph node biopsy from a patient who had progressed through all standard-of-care treatments for CRPC. (b) Schematic overview of CP50c PDX experimental design. Once CP50c PDX tumor volume reached 300mm³ treatment, administered by oral gavage, commenced with either vehicle or 20 mg/kg CCS1477 daily (QD) until reaching 300% of starting volume (long term, n=6 per group), with an additional subset treated for short term analysis at 8 days (n=4 per group for mRNA; n=3 for western blot). (c-d) Mean growth (normalized to start; defined as 100%) with standard error of mean was determined for each tumor. p-value (*p=<0.05, **p=<0.01, ***p=<0.001) was calculated for vehicle compared to CCS1477 at 20 mg/kg QD at 31 to 35 days using unpaired student t-test. (c). Time to reach 300% growth was used as a surrogate endpoint for survival. Hazard ratio (HR) with 95% confidence intervals and p-values for univariate cox survival model are shown (d). (e-f) The effect of 20mg/kg CCS1477 QD compared to vehicle at eight-days on AR, AR-V7, KLK3, TMPRSS2, and C-MYC mRNA expression (e) and on AR- FL, AR-V7, C-MYC, and GAPDH protein expression was determined (f). Mean mRNA expression (normalized to an average of B2M/GAPDH/HPRT1 and vehicle treatment; defined as 1.0) with standard error of mean from individual tumors in each group is shown. p-values (*p=<0.05, **p=<0.01, ***p=<0.001) were calculated for each treatment condition compared to vehicle using unpaired student t-test. (g) Gene set enrichment analysis of RNA-sequencing from vehicle group and 20mg/kg CCS1477 QD group at 8-days comparing the androgen response (left), AR signature (center left), AR-V7 signature (center right) and MYC targets V2 (right) with normalized enrichment score (NES) and false discovery rate (FDR) presented.