Buparlisib was well tolerated up to the 100 mg/day dose and showed preliminary activity in patients with advanced cancers. Future studies in more homogeneous patient populations will evaluate buparlisib in combination with other agents and further investigate the use of predictive biomarkers.

9004 Background: Capmatinib is a highly potent and selective MET inhibitor. Previous data of GEOMETRY mono-1 study showed a clinically meaningful overall response rate (ORR) and manageable toxicity profile in patients (pts) with METΔex14–mutated NSCLC who received 1–2 prior lines of treatment (tx) (Cohort 4) and in particular a high ORR in tx-naïve pts (Cohort 5b). Here we report the results in METΔex14–mutated NSCLC for duration of response (DOR) and progression-free survival (PFS) as well as the updated results for ORR. Methods: GEOMETRY mono-1 is a phase 2, multi-cohort, multicenter study evaluating capmatinib in pts with METΔex14-mutated or MET-amplified advanced NSCLC across 6 cohorts. Pts (≥18 yrs) with ECOG PS 0–1, ALK and EGFR wt, and stage IIIB/IV NSCLC were eligible. Pts with METΔex14 mutation (centrally confirmed) were assigned (regardless of MET amplification status/gene copy number) to Cohorts 4 and 5b and received capmatinib tablets 400 mg BID. Primary endpoint was ORR by Blinded Independent Review Committee (BIRC) per RECIST v1.1. Key secondary endpoint was DOR by BIRC. Results: As of Nov 08, 2018, 97 pts with METΔex14-mutated NSCLC (Cohort 4: 69 pts; Cohort 5b: 28 pts) were evaluable for efficacy. ORR (95% CI) by BIRC was 39.1% (27.6-51.6) in Cohort 4 and 71.4% (51.3-86.8) in Cohort 5b. While still immature at the time of this analysis, data on durability are promising: median DOR (95% CI) by BIRC was 9.72 (4.27-11.14) and 8.41 (5.55-NE) mo for Cohorts 4 and 5b, respectively; median PFS (95% CI) by BIRC was 5.42 (4.17-6.97) and 9.13 (5.52-13.86) mo for Cohorts 4 and 5b, respectively. Safety profile remains favourable and unchanged. Most common AEs (≥25% all grades) across all cohorts (n = 315), were peripheral edema (49.2%), nausea (43.2%), and vomiting (28.3%); majority of the AEs were grade 1/2. Final efficacy analysis (12-mo f-u on DOR) including biomarker data will be presented during meeting. Conclusions: These data confirm capmatinib to be a promising new treatment option for pts with METΔex14-mutated advanced NSCLC regardless of the line of therapy with deep and durable responses and manageable toxicity profile. Clinical trial information: NCT02414139.

In tumours that harbour wild-type p53, p53 protein function is frequently disabled by the mouse double minute 2 protein (MDM2, or HDM2 in humans). Multiple HDM2 antagonists are currently in clinical development. Preclinical data indicate that TP53 mutations are a possible mechanism of acquired resistance to HDM2 inhibition; however, this resistance mechanism has not been reported in patients. Utilizing liquid biopsies, here we demonstrate that TP53 mutations appear in circulating cell-free DNA obtained from patients with de-differentiated liposarcoma being treated with an inhibitor of the HDM2–p53 interaction (SAR405838). TP53 mutation burden increases over time and correlates with change in tumour size, likely representing selection of TP53 mutant clones resistant to HDM2 inhibition. These results provide the first clinical demonstration of the emergence of TP53 mutations in response to an HDM2 antagonist and have significant implications for the clinical development of this class of molecules.

Purpose: A first-in-human phase I study was conducted to characterize safety, efficacy, and pharmacokinetic (PK) and pharmacodynamic (PD) properties of lumretuzumab, a humanized and glycoengineered anti-HER3 monoclonal antibody, in patients with advanced cancer.Experimental Design: Twenty-five patients with histologically confirmed HER3-expressing tumors received lumretuzumab (100, 200, 400, 800, 1,600, and 2,000 mg) every two weeks (q2w) in 3þ3 dose-escalation phase. In addition, 22 patients were enrolled into an extension cohort at 2,000 mg q2w.Results: There were no dose-limiting toxicities. Common adverse events (any grade) included diarrhea (22 patients, 46.8%), fatigue (21 patients, 44.7%), decreased appetite (15 patients, 31.9%), infusion-related reactions (13 patients, 27.7%), and constipation (10 patients, 21.3%). The peak concentration (C max ) and area under the concentration-time curve up to the last measurable concentration (AUC last ) of lumretuzumab increased more than dose proportionally from 100 mg up to 400 mg. Linear PK was observed with doses !400 mg q2w indicating target-mediated drug disposition saturation. Downregulation of HER3 membranous protein was observed in ontreatment tumor biopsies from 200 mg, and was maximal at and above 400 mg. An ex vivo assay demonstrated increased activation potential of peripheral NK lymphocytes with lumretuzumab compared with a non-glycoengineered anti-HER3 antibody. Ten patients (21.3%) had stable disease and remained on study at a median of 111 days (range, 80-225 days).Conclusions: Lumretuzumab was well tolerated and showed evidence of clinical activity. Linear serum PK properties and plateauing of PD effects in serial tumor biopsies indicate optimal biologically active doses of lumretuzumab from 400 mg onwards.

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