A phase II multicenter biomarker trial to study the predictive value of TMPRSS2-ERG before enzalutamide treatment in chemo-naïve metastatic castration-resistant prostate cancer

5040

Background: TMPRSS2-ERG fusion gene is a common driver of prostate cancer. The PREMIERE study is a phase II, single arm open-label, multicentre, clinical trial designed to analyse the predictive/prognostic value of TMPRSS2-ERG in first-line chemo-naïve mCRPC patients treated with enzalutamide. Methods: We centrally evaluated TMPRSS2-ERG in diagnostic samples using PCR, FISH and IHC for ERG. Among exploratory biomarkers we included plasma DNA, AR copy number by ddPCR and CTC by AdnaTest. PCWG2 criteria were used for outcome evaluation. We correlated TMPRSS2-ERGand other exploratory biomarkers with mCRPC outcomes. Results: Ninety eight patients with median age 77 y (range 59-95), ECOG 0/1 (54/46%) with mts located in bone (82%), LN (48%) and visceral (17%). With a median FU of 37.3 months, PSA response was PSA50: 82% and PSA90: 53%; median PSA-PFS was 13.7m (95%CI 10.2-19.0), Rad-PFS 26.7m (95%CI: 22.0-NA) and OS 37.5m (95%IC: 33.7-NA). TMPRSS2-ERG was detected in 32 pts (33%), AR gain in 11 pts and CTCs in 35 pts. No differences were observed based on TMPRSS2-ERG status for PSA response (PSA50: 81% vs 83%; p=0.8), PSA-PFS (median 12.8 vs 14.7m; HR 0.98; 95%CI 0.58-1.67; p=0.95), Rad-PFS (median 28.4 vs 26.4m; HR 1.02; 95% 0.53-1.96, p=0.95) or OS (median 36.9 vs 38.1m; HR 1.23; 95%CI 0.69-2.21, p=0.48). Plasma AR gain was associated with worse PSA-PFS (median 4.2 vs 14.7 m; p<0.0001), Rad-PFS (median 3.6 vs 28.4m; p<0.0001) and OS (median 12.7 vs 38.1m; p<0.0001). Plasma DNA and CTCs were also associated with worse outcome. Multivariate analyses of exploratory biomarkers are included in the table. Conclusions: The fusion gene TMPRSS2-ERG is not predictive nor prognostic on enzalutamide treatment in first-line chemo-naïve mCRPC patients. Plasma AR gain and CTCs are strong independent biomarkers associated with adverse outcome. Multivariate analysis of exploratory biomarkers. Clinical trial information: NCT02288936. [Table: see text]

Cell plasticity associated to taxane-resistance in preclinical cell models and in circulating tumor cells from metastatic castration-resistant prostate cancer patients

238

Background: Treatment resistance is associated with tumor cells molecular plasticity. In metastatic castration resistant prostate cancer (mCRPC), alterations in androgen receptor (AR) have been described as predictors of shorter response to hormonal treatments. Previously, we associated epithelial to mesenchymal transition (EMT) phenotype with chemotherapy resistance. However, other molecular changes responsible of such resistance should be elucidated. Here, we investigate the effect of taxanes on cell plasticity through in vitro models and in circulating tumor cells (CTCs) from mCRPC patients. Methods: Molecular differences due to taxane-exposure were evaluated in cell models of mCRPC (PC-3 and DU-145 resistant to taxanes). Global gene expression (GE) analysis was performed using Affimetrix GeneChip Human Gene 2.0 arrays. GE related with AR axis, EMT and neuroendocrine (NE) phenotypes was validated by quantitative (qRT-PCR). Clinical validation was performed in CTCs from 24 mCRPC patients collected prior and post taxane-treatment. CTCs enrichment was achieved by Isoflux technology through a personalized combination of EpCAM, CDH2 and PSCA antibodies. Results: GE analysis revealed a different deregulation pattern related to the EMT, NE and AR-related phenotypes in resistant CRPC-cells compared to parental cells. Docetaxel resistance was more associated to an EMT phenotype while cabazitaxel resistance to NE patterns. GE patterns in CTCs at post taxane-treatment showed a common upregulation of AR-related genes compared to pre-treatment collected samples. Moreover, most patients experienced upregulation of EMT and NE markers after treatment, which was more pronounced after docetaxel than cabazitaxel therapy. Conclusions: GE changes related to taxane-resistance observed in pre-clinical models also occur in CTCs. This supports the great value of CTCs to evaluate cell plasticity due to taxanes treatment. Further investigation is ongoing to better characterize cellular plasticity and to improve personalized therapeutic strategies that would enhance better clinical outcomes in mCRPC.

The influence of treatment sequence in the prognostic value of TMPRSS2-ERG as a biomarker of taxane resistance in castration-resistant prostate cancer

235

Background: TMPRSS2-ERG expression at peripheral blood has been correlated with lower docetaxel benefit. This multicenter study prospectively assessed the role of TMPRSS2-ERG mRNA as a taxane-resistance biomarker in blood and retrospectively in tumors, and explored the impact of prior abiraterone/enzalutamide (A/E) in castration-resistant prostate cancer (CRPC) patients and in vitro. Methods: TMPRSS2-ERG was tested by quantitative reverse-transcription PCR. We included 204 patients (137 blood and 124 tumor samples) treated with taxanes. TMPRSS2-ERG expression was correlated with PSA-progression-free survival (PFS), radiological-PFS (RX-PFS), and overall survival (OS). Independent association with survival was evaluated by multivariate Cox modeling. ERG knockdown, combinatorial and sequential experiments with enzalutamide and docetaxel were performed in VCaP cells. Results: In the multivariate analysis prior A/E (HR: 1.833; P = 0.005) and blood TMPRSS2-ERG (HR: 2, 95%CI; 1.1-3.67; P = 0.018) , were independently associated to lower PSA-PFS. In patients without prior A/E, both blood and tumor TMPRSS2-ERG independently predicted lower PSA-PFS (HR 2.92; P = 0.014 and HR 1.82; P = 0.045, respectively) to taxanes. This was not observed in patients with prior A/E. There was a significant interaction between blood TMPRSS2-ERG detection and prior A/E related to PSA-PFS (P = 0.032) and RX-PFS (P = 0.009). In vitro stable ERG inhibition did not sensitize VCaP cells to docetaxel. Concomitant enzalutamide and taxanes were synergistic, but prior enzalutamide reduced docetaxel cytotoxicity in VCaP cells. Enzalutamide induced neuroendocrine markers and reduced E-cadherin expression. Conclusions: Prior hormone-therapy may influence taxanes response and TMPRSS2-ERG prognostic value. Thus, multiple and sequential biomarkers are needed in CRPC follow-up evaluation.

ARV7 and ARFL mRNA in blood to predict androgen receptor inhibitors and docetaxel response in castration-resistant prostate cancer patients

207

Background: The constitutively active androgen receptor (AR) variant 7 ( ARV7) has been associated with AR inhibitors (ARI) resistance, while its role predicting taxanes response remains controversial. We investigated the association between ARV7 and AR full length ( ARFL) expression pre-docetaxel treatment and changes pre- post-treatment in blood with docetaxel activity in metastatic castration-resistant prostate cancer (mCRPC) patients. Methods: ARV7 and ARFL mRNAs were tested by quantitative reverse-transcription PCR in peripheral blood mononuclear cells (PBMC) from mCRPC patients. Measurements were performed before docetaxel treatment and in a subset of patients also post-treatment. A cohort of patients treated with ARI was also included as a control. Results: We included 105 patients: 50 with treated with docetaxel and 55 with ARI. In 28 patients ARV7 and ARFL were evaluated pre and post-docetaxel. High ARV7 correlated with longer PSA-PFS (HR 0.42; 95%CI 0.18-0.99; P= 0.049), radiologic (RX)-PFS (HR 0.32; 95%CI 0.14-0.72; P= 0.006), and overall survival (OS) (HR 0.41; 95%CI 0.18-0.91; P= 0.028) to docetaxel. When relativizing to ARFL we observed that high ARV7/ ARFL ratio also correlated with a better PSA-PFS (HR 0.38; 95%CI 0.17-0.85; P= 0.0179) and RX-PFS (HR 0.43; 95%CI 0.2-0.91; P= 0.0273) to docetaxel. High ARV7 and ARV7/ ARFL were correlated with lower prostatic-specific antigen (PSA) progression-free survival (PFS) to ARI therapy (HR 2.18; 95%CI 1.03-4.6; P= 0.043 and HR 3.84; 95%CI 1.54-9.4; P= 0.004, respectively). ARV7/ ARFL and treatment- ARV7/ARFL interaction were independently associated with better PSA-PFS to docetaxel treatment and lower PSA-PFS to ARI. The increase of ARV7 mRNA levels after docetaxel treatment was indicative of longer OS (HR 0.07; 95%CI 0.008-0.57; P= 0.013). Conclusions: High ARV7 expression and ARV7/ ARFL ratio evaluated in PBMC pre-docetaxel are associated with better clinical outcome in mCRPC patients and lower ARI benefit. The increase of ARV7 levels after docetaxel exposure was also indicative of better outcome.

Treatment efficacy of abiraterone (abi), enzalutamide (enza) or cabazitaxel (caba) in metastasic castration-resistant prostate cancer patients (mCRPC) after progression to docetaxel plus androgen deprivation therapy (ADT) in hormone sensible disease

198

Background: Different treatments efficacy for mCRPC when progression after docetaxel x 6 cycles + ADT (as CHAARTED scheme) are unknown as all pivotal trials where performed in patients who progressed to mCPRC after ADT. Methods: A retrospective analysis of 175 mCRPC patients of 10 spanish hospitals who were treated with docetaxel + ADT as first line treatment was performed. Patients characteristics at diagnosis (age, gleason) and at progression to mCRPC were analyzed (PSA, presence of visceral mets, type of progression). As efficacy endpoints, clinical and objective response, and survival from progression to mCRPC were analyzed. Results: Median age at diagnosis 65.2 years old (range 44-84). Metastatic at diagnosis 173. Bone metastasis 155 (88,5%), visceral 31 (17.7%), gleason >7 130 (74,3%), number docetaxel cycles: 6 (80%), 5 (5,7%), <5 (14,3 %). Median survival from diagnosis: 35 months. Progression to CRPC 78pts (44.5%) Type of progression: PSA 74/78 (94,9%), clinical 45/78 (57.7%), radiological 59/78 (75.6%). Median survival from progression to CRPC: 10.3 months. Treatments frequency, clinical benefit (RP/EE) and median survival: abi 30 (38.4%)/ 7(23.3%)/ 15.7 m; enza 12 (15.4%)/ 4 (33.3%)/ 10.4 m, caba 14(17.9%)/ 3(21.4%)/ 6.4m; Other treatments frequency: Ra223 4 (5.1%), docetaxel 4 (5.1%), others/no treatment/BSC 14 (17.8%). Clinical and radiological progression before treatment was 36.7%/63.3% in abi patients, 58.3%/63.7% in enza and 93.9%/93.9% in caba pts. Visceral (mostly hepatic) metastasis were more frequent in caba (57.1%) than in abi (11.8%) or enza (0%) pts. Median PSA value abi 375/ caba 1633. Conclusions: Although AA seems be more effective than cabazitaxel in mCRPC progressed after docetaxel + ADT in HSPC, patients treated with caba are of worse prognosis.

In geriatric evaluation, some iadl (Katz) scale items are more predictive of efficacy and toxicity than ADL (Lawton) scale or Charlson Comorbidity Index in metastasic castration-resistant protate cancer (mCRPC) patients treated with cabazitaxel in a weekly schedule

176

Background: Cabazitaxel (CBZ) improves overall survival in mCRPC that progresses during or after docetaxel treatment. CABASEM is a phase II study to evaluate the efficacy and safety of a weekly schedule of CBZ for 'unfit' (ECOG2, previous neutropenic fever with docetaxel, or radiotherapy to <25% of areas of bone marrow reserve) mCRPC patients after docetaxel failure. Fragility scales were performed to patients included before treatment and results are described. Methods: All 70 patients were treated with CBZ 10 mg/m2/wk 4 administration every 5 weeks. Geriatric fragility scales performed were Lawton daily day activities (ADL), BPI score, Katz instrumental daily day activities (IADL) and Charlson index. General and specific items have been analyzed in relation with toxicity and efficacy (clinical benefit (OR+SD), PSA response, composite PFS, PSA-PFS, and overall survival) in all patients and in older than 70 years. Results: Median age 73 (range 54-85). Charlson index and ADL scale had not relationship with any toxicity observed and any efficacy outcome in the whole group nor in older than 70. IADL independence grade was related to survival in the whole group (p=0,025) and older than 70 (p=0,02). In the whole group, some IADL items were associated with PSA response (buying, p=0.003; cooking, p=0.06; and IADL independence grade p=0.01), PSA PFS (telephone use, p=0.01; handle finances, p=0.06), composite PFS (telephone use, p=0.013; housekeeping, p=0.03; handle finances, p=0,06) and OS (telephone use p=0.001; laundry, p=0.008; handle finances, p=0.02 and IADL dependence grade, p=0.003). Only any grade diarrhea and grade 2 neutropenia was associate with buying (p=0.025) and cooking (p=0.05) IADL items respectively, in patients older than 70 years. Conclusions: IADL scale and items seem to be more related to efficacy (OS, PSA response, PFS, clinical benefit and PSA PFS) than ADL and Charlson scales in mCRPC older than 70 years treated with weekly cabazitaxel. No clear association of scales and items with toxicity were observed in this group of patients. Clinical trial information: NCT01518283.

Fierce-21: Phase II study of vofatmab (B-701), a selective inhibitor of FGFR3, as salvage therapy in metastatic urothelial carcinoma (mUC)

409

Background: Patients (pts) with mUC who have failed platinum-based chemotherapy have a poor prognosis. About 20% of them usually respond to immune checkpoint inhibitors (ICI). Also, 20% of pts with mUC harbor FGFR3 mutations or fusions (M/F), and this feature may be associated with lower sensitivity to ICI. Vofatamab (B-701) is a fully human monoclonal antibody against FGFR3 that blocks activation of the wildtype and genetically activated receptor. FIERCE-21 is a Phase 1b/2 study designed to evaluate vofatamab monotherapy (VM) or in combination with docetaxel (VD). Methods: The study consists of a P 1b lead-in (P1b with VD), previously reported followed by P2 expansion cohort in FGFR3 M/F+ pts (identified with the FoundationONE CDx™ assay on archival samples). The study enrolled mUC pts with failure to ≥ 1 line prior chemotherapy (including prior taxane treatment) or ≤12 months of (neo)adjuvant chemotherapy, measurable disease and ECOG ≤ 1. Treatment consisted of vofatamab at 25 mg/kg alone (VM) and in combination with D (VD) at 75 mg/m2 q3w. Efficacy was assessed by investigators (RECIST 1.1). Primary objectives were safety and activity (objective response-rate [ORR]). Results: 55 pts have received treatment. In the Ph 2 study, 21 pts received VM, 15 pts received VD. 35% of pts were included as 2nd line therapy, 65% in 3rd or later line of treatment. For pts receiving VD, safety was consistent with Ph 1B data. For pts receiving VM, median age was 67 yrs, ECOG 1 = 71.4%, Hgb < 10 gm/dL 13%, liver metastases 19%, ≥ 2 prior regimens 57%, (best response to prior therapy PD 31%). TEAEs occurring in ≥5% patients were asthenia (19%), diarrhea (9.5%), flushing 14%, chills (9.5%), hypotension (9.5%), decreased appetite (19%) and creatinine increased (9.5%). The majority of TEAS were grade 1 and 2. Only 1 patient on MF had a grade 3 TEAE and only 1 patient discontinued treatment due to an AE. The ORR have been seen in 7 pts to date including those receiving both VM and VD. Conclusions: Vofatamab both alone and combined with D in an every 3-week schedule are well tolerated with a low frequency of grade 3 TEAEs. Both VM and VD have demonstrated efficacy in terms of ORR, and mature results with PFS data will be presented. Clinical trial information: NCT02401542.

A phase I-II study to evaluate safety and efficacy of the combination of niraparib plus cabozantinib in patients with advanced kidney/urothelial carcinoma

TPS501

Background: Niraparib (N) is an orally selective poly(ADP-ribose) polymerase (PARP)-1/-2 inhibitor approved for maintenance treatment of patients (pt) with recurrent epithelial ovarian, fallopian tube, or primary peritoneal cancer after complete or partial response to platinum-based chemotherapy (CT). Cabozantinib (C) is a tyrosine kinase (TK) inhibitor with activity against TKs including VEGFR2, MET and AXL, approved on kidney cancer pt after TK failure, that has demonstrated clinical activity in heavily pretreated, advanced UC pt. c-Met receptor TK is activated in urothelial carcinoma (UC) cells. c-Met activity can decrease response to PARP inhibitors, whereas treatment with c-Met inhibitors renders cells more sensitive to PARP inhibition. UC pt with tumors overexpressing c-Met may benefit from the combination of c-Met and PARP inhibitors. This multicenter, open-label phase (ph) I-II study is to explore the maximum-tolerated dose (MTD) of N + C combination in pt with advanced genitourinary malignancies (UC and kidney cancer) follow by a preliminary efficacy of the combination in advanced UC. Methods: Eligible pt have confirmed histopathology of UC or clear cell renal cell carcinoma, advanced or metastatic disease, age ≥18 years, ECOG PS ≤1, progressive disease after platinum-based CT, measurable lesions, no prior therapy with PARP or c-Met inhibitors and adequate bone marrow, liver and renal functions. The ph I portion is enrolling ≈24 pt to identify the MTD proposed to use in a ph II (RP2D). Pt will receive N and C p.o. once daily in 28-day cycles: Dose level 1 (DL1) N/C 100/20 mg; DL2 200/20 mg; DL3 200/40 mg; DL4 200/60 mg. Pt will be accrued to each dose level in cohorts of 6 pt until the MTD is achieved (the highest dose at which ≤1 out of 6 pt experience a dose-limiting toxicity [DLT]). DLT will be evaluated during the first 2 cycles. The ph 2 portion will enroll 51 UC pt to receive the RP2D. Tumor response will be assessed per RECIST v1.1. Endpoints of the ph 2 are 6-month PFS (primary), overall response rate, disease control rate, duration of response, PFS and OS. Tissue and plasma sample will be collected for translational study. Clinical trial information: NCT03425201.

Plasma AR status and cabazitaxel in heavily-treated metastatic castration-resistant prostate cancer (mCRPC)

203

Background: Plasma androgen receptor ( AR) copy number status has been identified as a potential biomarker of response in mCRPC patients receiving docetaxel or the AR-targeted therapies abiraterone or enzalutamide. However, the relevance of plasma AR status in the context of cabazitaxel therapy is unknown. Methods: Between September 2011 and January 2018, pre-therapy plasma samples were collected from 155 patients treated with second or third-line cabazitaxel at standard or reduced dose in different biomarker protocols. Droplet digital PCR was used to identify plasma AR gain and normal samples, with the primary objective to evaluate associations of plasma AR status with treatment outcome. In an exploratory analysis, a comparison between plasma AR status and treatment type was investigated by incorporating updated data from our prior study of 85 post-docetaxel patients receiving abiraterone or enzalutamide. Results: We observed a shorter median overall/progression-free survival (OS/PFS) in AR-gained compared to AR-normal patients (OS 10.5 versus 14.1 months, hazard ratio (HR) 1.44, 95% confidence interval (CI) 0.98-2.13, P = 0.064), and (PFS 4.0 versus 5.0 months, HR 1.47, 95%CI 1.05-2.07, P = 0.024). In mCRPC patients receiving second-line therapies, a significant treatment interaction was observed between plasma AR and cabazitaxel versus AR-directed therapies for OS (P = 0.041) but not PFS (P = 0.244). In an exploratory analysis, AR-gained patients treated with initial reduced-dose of cabazitaxel had a significantly shorter median OS (7.3 versus 11.5 months, HR 1.95, 95%CI 1.13-3.38, P = 0.016), and PFS (2.7 versus 5.0 months, HR 2.27, 95%CI 1.39-3.71, P = 0.001). Conclusions: Plasma AR status has a potential clinical utility in patients being considered for cabazitaxel. Validation of these findings in prospective trials are warranted.

Acute tubulointerstitial nephritis associated with atezolizumab, an anti-programmed death-ligand 1 (pd-l1) antibody therapy

Direct stimulation of the antitumor activity of immune system through checkpoint inhibitors (ICIs) has demonstrated efficacy in the treatment of different cancer types. The activity of these antibodies takes place in the immunological synapse blocking the binding of the negative immunoregulatory proteins, thus leading to the finalization of the immune response. Despite having a favorable toxicity profile, its mechanism of action impedes the negative regulation of the immune activity which can potentially favor autoimmune attacks to normal tissues. Renal toxicity has been described in several ICI but not with atezolizumab, an IgG1 monoclonal antibody targeting PD-L1 (programmed death ligand 1), approved by FDA as a second-line therapy for advanced urothelial carcinoma. Here we present a patient with a single kidney and metastatic renal cell carcinoma treated with atezolizumab and bevacizumab combination, with biopsy-proven acute interstitial nephritis, who had a complete resolution of renal dysfunction after steroid therapy.

Erdafitinib (ERDA; JNJ-42756493), a pan-fibroblast growth factor receptor (FGFR) inhibitor, in patients (pts) with metastatic or unresectable urothelial carcinoma (mUC) and FGFR alterations (FGFRa): Phase 2 continuous versus intermittent dosing

411

Background: Although immune checkpoint inhibitors (ICI) have improved outcomes in some pts with platinum-resistant mUC, many pts (eg, pts with TCGA luminal 1 tumors, many of whom are FGFRa) may not benefit. ERDA, a pan-FGFR (1-4) inhibitor, demonstrated promising phase 1 activity: 11 partial responses among 24 FGFRa mUC pts. We report efficacy and safety of ERDA in the ongoing global open-label phase 2 study BLC2001 (NCT02365597). Methods: Pts had measurable mUC with specific FGFR2/ FGFR3 mutations or translocations per central lab Janssen assay, ECOG 0-2, and were chemorefractory (progressed during/following ≥ 1 line of prior systemic chemo or ≤ 12 mos of [neo]adjuvant chemo). Cisplatin-ineligible, chemo-naïve pts, and prior ICI treatment were allowed. Pts were randomized 1:1 to 28-d cycles of oral 6 mg/d continuous dosing (6 C) or 10 mg/d intermittent 7 d on/7 d off dosing (10 I) ERDA; the dose was further uptitrated if no significant treatment-related adverse events (TRAEs) were observed. The primary end point was ORR. Results: 78 pts received 6 C and 33 pts received 10 I (10 I cohort stopped early) ERDA. 31 pts in 6 C arm were further uptitrated. Across arms, 50% had ≥ 2 prior lines of therapy; 93% were chemorefractory. Confirmed ORRs (RECIST 1.1) were 35% and 24%, and disease control rates (CR+PR+SD) were 74% and 73% in the 6 C and 10 I arms, respectively. Adverse events (AEs) were manageable, and there were no treatment-related deaths (Table). Treatment is ongoing in 10 pts. Conclusions: ERDA (6 C or 10 I) has promising efficacy and tolerability in pts with FGFRa mUC. Based on these results and ERDA pharmacometric modeling, dosing was optimized at 8 mg/d (continuous), and this cohort is ongoing. Phase 3 study is planned. Clinical trial information: NCT02365597. [Table: see text]

A phase Ib open-label, dose escalation and expansion study to investigate the safety, pharmacokinetics, pharmacodynamics and clinical activity of GSK525762 in combination with abiraterone or enzalutamide in metastatic castrate-resistant prostate cancer

TPS391

Background: Metastatic castrate-resistant prostate cancer (mCRPC) remains an incurable illness as resistance develops after androgen deprivation therapy (ADT) and/or androgen receptor (AR) axis targeted therapies. The bromodomain (BRD) and extraterminal (BET) proteins are critical for transcription. Preclinically, one of these proteins, BRD4, acts in complex with AR to mediate androgen signaling that leads to prostate cell growth and proliferation. GSK525762 is an oral pan-BET inhibitor that suppresses BET dependent activated AR-driven transcription. Combined with androgen production or receptor targeted agents like abiraterone or enzalutamide, GSK525762 may enhance efficacy of or overcome resistance to either agent. Methods: This is a Phase Ib open-label, dose-escalation study to evaluate the safety and efficacy of oral administration of GSK525762 in combination with either abiraterone plus prednisone (Arm A) or enzalutamide (Arm B) in mCRPC patients whose disease has progressed on prior abiraterone or enzalutamide. Patients must have documented prostate cancer progression as assessed by rising PSA or radiographic progression of soft tissue by PCWG3-modified RECIST 1.1 criteria or bone metastasis. Dose escalation is designed to identify safe doses to move into dose expansion. Dose expansion will explore safety and efficacy in patients who failed in first line (L2 population) or after multiple lines of prior therapy (LX population). Primary objectives include defining the safety, tolerability and clinical activity of GSK525762 when combined with products in Arm A or Arm B. Primary clinical activity endpoint is defined as the response rate of subjects achieving a 50% or more reduction from baseline of PSA at 12 weeks or thereafter. Dose escalation will employ a modified Toxicity Probability Interval (mTPI) design. Dose expansion will use a Bayesian adaptive design, which will calculate posterior probability that utility of the dose is clinically significant at interim futility analysis for each dose level. Funding: GSK Clinical trial information: NCT03150056.

Phase II trial of afatinib in patients with advanced/metastatic urothelial carcinoma (UC) with genetic alterations in ERBB receptors 1-3 who failed on platinum-based chemotherapy (CT)

TPS540

Background: First-line treatment of patients (pts) with advanced/metastatic UC consists of platinum-based CT, with no well-established subsequent therapy for platinum-refractory disease. Although checkpoint inhibitors have shown promising results recently, targeted agents have generally not demonstrated significant clinical activity in this setting. Around 20% of UC harbor ERBB family genetic alterations, as such it may be a suitable therapeutic target (Knowles, Nat Rev Cancer 2015;15:25–41). The irreversible ERBB family blocker, afatinib, has shown activity in a Phase II trial in a subset of pts with UC who had ERBB2/ERBB3 aberrations (Choudhury, J Clin Oncol 2016;34:2165–71). This Phase II trial will evaluate afatinib in pts with UC molecularly selected for ERBB receptor alterations. Methods: This single-arm trial will assess the efficacy and safety of afatinib in pts with UC harboring ERBB2/ERBB3 mutations or ERBB2 amplification (Cohort A), or EGFR (ERBB1) amplification (Cohort B). Eligible pts are ≥18 years of age with ECOG PS 0–1, histologically confirmed advanced/metastatic UC of the bladder, upper tract or urethra, not amenable to surgery and progressing during or after platinum-based CT, with available archival tissue samples for pre-screening biomarker analysis. Pts will receive oral afatinib 40 mg/day until disease progression or discontinuation. Cohort A is enrolling in two stages, with Stage 2 enrollment based on anti-tumor activity observed. The primary endpoint is progression-free survival (PFS) rate at 6 months; secondary endpoints include objective response rate, PFS, overall survival, disease control rate, duration of response and tumor shrinkage. Trial objectives will be analyzed separately for the two cohorts. Safety and biomarker assessments will also be performed. The trial commenced in June 2016; as of October 4, 2017, 201 samples have been analyzed, with 24.3% and 8% of pts with genetic alterations potentially eligible for inclusion in Cohort A and B, respectively. To date, 12 pts have received study treatment in Cohort A and 6 in Cohort B; recruitment is ongoing. Clinical trial information: NCT02780687.

ARV7/AR ratio and neutrophil-to-lymphocyte ratio (NLR) as predictors of docetaxel benefit in metastatic castration-resistant prostate cancer patients (mCRPC)

254

Background: The constitutively active androgen receptor (AR) variant 7 (ARV7) has been associated to AR inhibitors resistance, but its role in taxane-benefit has not been stablished. Moreover, the neutrophil-to-lymphocyte ratio (NLR) has been associated with poor outcome in prostate cancer.The PBMC population may contain circulating tumor cells (CTCs) but is mainly constituted by lymphocytes and monocytes, that also express the AR. Here we studied the expression of ARV7 and AR in peripheral blood mononuclear cells (PBMC) and its correlation with NLR and clinical outcome in mCRPC treated with docetaxel. Methods: ARV7 and AR mRNAs were tested by quantitative reverse-transcription PCR. Baseline neutrophil and lymphocyte values and PBMC samples were prospectively collected before treatment initiation. Patients were stratified according to NLR ratio (low NLR: ≤3; high NLR:>3) and to ARV7/ARFL ratio expression (Maxstat Cutoff 1.99). Correlation between NLR and PSA progression-free (PSA-PFS) and overall survival (OS), were measured from the start of docetaxel treatment and calculated by log rank test. Results: Fifty patients were included:25 (50%) had low NLR. Thirty-eight patients (76%) expressed high ARV7/ARFL. No significant correlation between NLR with ARV7, AR and ARV7/AR was observed. High ARV7/ARF ratio correlated to a better PSA-PFS (median PSA-PFS 7.47; HR 0.38, 95%CI 0.17-0.85; P=0.0179) , but not OS. High NLR was associated to a lower OS [Median OS was 9.2 months versus 30.17 months in those with low NLR (HR 2.19, 95% CI 1.17-4.09, p= 0.01)]. When both parameters were combined, high NLR and low ARV7/ARFL ratio were associated to a worse PSA-PFS in comparison with low NLR and high ARV7/ARFL ratiogroup(median PSA-PFS: 4.9 vs. 7.5; p=0.008 and HR 5.08, 95% CI 1.33-19.41, p= 0.08) and OS (median OS: 7.4 vs. 30.5; p=0.001 and HR 22.79, 95% CI 4.29-121.17, p= 0.00). Conclusions: The combination of low ARV7/ARFL high NLR and ratio evaluated in PBMC prior to docetaxel treatment has a predictive impact on response and survival in mCRPC patients.