Clinical activity of avapritinib in ≥ fourth-line (4L+) and PDGFRA Exon 18 gastrointestinal stromal tumors (GIST)

11022

Background: Targeting oncogenic KIT and PDGFRA mutations revolutionized treatment of patients (pts) with advanced GIST; however, nearly all pts succumb to resistant disease. Avapritinib is a potent and selective kinase inhibitor with broad activity against oncogenic KIT/PDGFRA mutants, including PDGFRA D842V and other primary or secondary resistance mutations. Updated results from the phase 1 NAVIGATOR (NCT02508532) study of avapritinib in pts with advanced GIST are presented. Methods: Adult pts with unresectable PDGFRA D842V or other mutant GIST who progressed on imatinib and ≥ 1 other tyrosine kinase inhibitor (TKI) were treated with oral, daily, continuous avapritinib. Adverse events (AE) and response by mRECIST 1.1 per central radiology were assessed. Safety from the overall population (30-600 mg doses) and efficacy in the response evaluable 4L+ and PDGFRA Exon 18 (Ex 18) populations treated at the MTD (400 mg)/RP2D (300 mg) were analyzed. Results: As of 16 Nov 2018, 237 pts [172 KIT, 62 PDGFRA Ex 18 (56 D842V, 6 non-D842V), 2 PDGFRA N659K, 1 missing] were enrolled including 111 in the 4L+ population (primarily KIT, median 4 prior TKI) and 43 in the Ex 18 population (median 1 prior TKI). The 4L+ ORR was 22% [1 CR, 23 PR (1 pending)], and 52 SD with median duration of response (mDOR) of 10.2 months (95% CI: 7.2-NE). The Ex 18 ORR was 86% [3 CR, 34 PR (1 pending)] and 5 SD; mDOR was not reached (95% CI: 11.3-NE). Most AE were grade 1-2, most commonly nausea (63%), fatigue (58%), anemia (49%), periorbital edema (42%), diarrhea (40%), vomiting (40%), decreased appetite (38%), increased lacrimation (33%), peripheral edema (33%) and memory impairment (most common cognitive AE, 29%). 10% of pts discontinued due to a related AE. Grade 3-4 related AE ≥ 2% were anemia, fatigue, hypophosphatemia, hyperbilirubinemia, neutropenia, and diarrhea. Conclusions: Avapritinib has important clinical activity in pts with advanced GIST who have no effective therapies. The ORR and DOR of avapritinib in 4L+ exceeds that of approved 2nd and 3rd line therapies and shows unprecedented activity in D842V and other Ex 18 mutant PDGFRA GIST. Results suggest avapritinib has the potential to change the treatment paradigm of pts with advanced GIST. Clinical trial information: NCT02508532.

Subgroup analysis by baseline (BL) weight-associated parameters: A phase III study of liposomal irinotecan (nal-IRI)±5-fluorouracil/leucovorin (5-FU/LV) in patients (pts) with metastatic pancreatic ductal adenocarcinoma (mPDAC) previously treated with gemcitabine-based (gem) therapy

410

Background: We report prognostic evaluation of BL weight-associated parameters (body-mass index [BMI], body surface area [BSA] and weight) in pts with mPDAC after progression following gem-based therapy (NAPOLI-1 trial; NCT01494506). Pts received nal-IRI+5-FU/LV, nal-IRI monotherapy or 5-FU/LV in NAPOLI-1, an international, randomised, phase 3 trial; nal-IRI+5-FU/LV treatment resulted in a 45% increased median OS vs. 5-FU/LV (unstratified HR = 0.67; p = 0.012). Methods: This exploratory subgroup analysis compares outcomes by BL BMI, BSA and weight, using primary survival analysis data from the ITT population for all treatment arms combined (n = 417) and the nal-IRI+5-FU/LV arm on its own (n = 117). Results: OS and PFS were not significantly different between BL BMI, BSA and weight median subgroups in the entire NAPOLI-1 ITT population (HR range 1.06–1.15; log-rank p-value range 0.21–0.60; Table) and in the nal-IRI+5-FU/LV arm (HR range 0.94–1.19; log-rank p-value range 0.43–1.00). Conclusions: This post-hoc subgroup analysis did not detect any prognostic impact on treatment outcome by BL BMI, BSA and weight for mPDAC pts progressed following gem-based therapy. This observation rules out a treatment-independent effect. No evidence of a predictive effect on nal-IRI+5-FU/LV efficacy was found. Clinical trial information: NCT01494506. [Table: see text]

Subgroup analysis by prior lines of metastatic therapy (mtx) in NAPOLI-1: A global, randomized phase 3 study of liposomal irinotecan (nal-IRI) ± 5-fluorouracil and leucovorin (5-FU/LV), vs. 5-FU/LV in patients (pts) with metastatic pancreatic ductal adenocarcinoma (mPDAC) who have progressed following gemcitabine-based therapy

4127

Background: In the NAPOLI-1 study, nal-IRI+5-FU/LV significantly increased median OS vs. 5-FU/LV control (6.1 vs. 4.2 mo; unstratified HR = 0.67 [0.49–0.92]; p = .012). This is a subgroup analysis by prior lines of mtx. Methods: Study methodology has been published (Wang-Gillam; Lancet 2016). This exploratory subgroup analysis compares outcomes in pts with 0–1 vs. ≥2 prior mtx lines, based on primary survival analysis data (cut-off February 2014) of the ITT population. Results: OS, PFS and CA19-9 response rates in pts with 0–1 (65.8% of pts) or ≥2 (34.2%) prior mtx lines are shown (see Table). Median OS for nal-IRI+5-FU/LV improved vs. 5-FU/LV by 2.1 mo to 6.2 mo (HR = 0.66; p = .03) in pts with 0–1 prior mtx lines and by 1.1 mo to 5.4 mo (HR = 0.68; p = .18) in pts with ≥2 prior mtx lines. The safety profile was similar between subgroups with nal-IRI+5-FU/LV (≥grade 3 drug-related AEs: 43 [55%] with 0–1 and 20 [51%] with ≥2 prior mtx lines). Conclusions: This post-hoc subgroup analysis shows significant increases for nal-IRI+5-FU/LV over 5-FU/LV in OS, PFS and CA19-9 response in pts with 0–1 prior mtx lines. Median OS benefit was less prominent in later lines, but conclusions are restricted by limited pt numbers. Clinical trial information: NCT01494506. [Table: see text]

Androgen Receptor Modulation Optimized for Response in Splice Variant (ARMOR3-SV): Randomized, open-label, multicenter, controlled study of galeterone versus enzalutamide (enz) in men expressing AR-V7 splice variant (SV), metastatic castrate resistant prostate cancer (mCRPC)

259

Background: Recent data showed that mCRPC patients (pts) with the androgen receptor (AR) SV AR-V7, a truncated form of the AR that lacks the ligand-binding domain and remains a constitutively active transcription factor, had worse clinical outcomes than patients without AR-V7 (Antonarakis et al, NEJM 2014; Efstathiou et al, ASCO 2014; Bambury et al, ESMO 2014). Galeterone, a small molecule, disrupts AR signaling via selective inhibition of CYP17 lyase, competitively inhibits androgen binding to AR, and degrades AR protein. In preclinical models, it demonstrated activity against many AR aberrations, including AR-V7, ARv567es, AR-T878A, and AR-F876L. Given the encouraging results in pts with AR C-terminal loss in the phase 2 ARMOR2 trial (Taplin et al, ESMO 2014), further research is warranted. Methods: ARMOR3-SV is a global, phase 3, randomized, open-label, multicenter, controlled study of galeterone vs enz in men expressing AR-V7 SV–mCRPC. Among other enrollment criteria, eligible pts must have the AR-V7 splice variant, be on GnRH therapy or have had a bilateral orchiectomy with testosterone <50 ng/dL. Approximately <170 pts will be randomized to receive once-daily oral therapy with galeterone 2550 mg or enz 160 mg. The primary endpoint is radiographic progression-free survival. Secondary endpoints include overall survival, time to cytotoxic therapy, and skeletal related events. Pts will be followed until radiographic disease progression as assessed by an independent, blinded radiologic review. Post-progression anticancer interventions will be collected and pts will be followed until death or study termination. Results: Because AR-V7 status must be determined for enrollment, the availability of a validated, accurate, rapid, quantitative, and universally applicable assay performed in a central CLIA-certified laboratory is critical to the trial. Conclusions: Choice of assay to identify and select mCRPC pts harboring AR-V7 is key to enrollment strategy for ARMOR3-SV. The study is expected begin in the first half of 2015.