A phase II study of a human anti-PDGFRα monoclonal antibody (olaratumab, IMC-3G3) in previously treated patients with metastatic gastrointestinal stromal tumors

Ann Oncol. 2017 Mar 1;28(3):541-546. doi: 10.1093/annonc/mdw659.

Abstract

Background: This study evaluated tumor response to olaratumab (an anti-PDGFRα monoclonal antibody) in previously treated patients with metastatic gastrointestinal stromal tumor (GIST) with or without PDGFRα mutations (cohorts 1 and 2, respectively).

Patients and methods: Patients received olaratumab 20 mg/kg intravenously every 14 days until disease progression, death, or intolerable toxicity occurred. Outcome measures were 12-week tumor response, progression-free survival (PFS), overall survival (OS), and safety.

Results: Of 30 patients enrolled, 21 patients received ≥1 dose of olaratumab. In the evaluable population (cohort 1, n = 6; cohort 2, n = 14), no complete response (CR) or partial response (PR) was observed. Stable disease (SD) was observed in 3 patients (50.0%) in cohort 1 and 2 patients (14.3%) in cohort 2. Progressive disease (PD) was observed in 3 patients (50.0%) in cohort 1 and 12 patients (85.7%) in cohort 2. The 12-week clinical benefit rate (CR + PR + SD) (90% CI) was 50.0% (15.3-84.7%) in cohort 1 and 14.3% (2.6-38.5%) in cohort 2. SD lasted beyond 12 weeks in 5 patients (cohort 1, n = 3; cohort 2, n = 2). Median PFS (90% CI) was 32.1 (5.0-35.9) weeks in cohort 1 and 6.1 (5.7-6.3) weeks in cohort 2. Median OS was not reached in cohort 1 and was 24.9 (14.4-49.1) weeks in cohort 2. All patients in cohort 1 and 9 (64.3%) in cohort 2 experienced an olaratumab-related adverse event (AE), most commonly fatigue (38.1%), nausea (19.0%), and peripheral edema (14.3%). Two grade ≥3 olaratumab-related events were reported (cohort 1, syncope; cohort 2, hypertension).

Conclusions: Olaratumab had an acceptable AE profile in patients with GIST. While there was no apparent effect on PFS in patients without PDGFRα mutations, patients with PDGFRα-mutant GIST (all with D842V mutations) treated with olaratumab had longer disease control compared with historical data for this genotype.

Clinicaltrials.gov identifier: NCT01316263.

Keywords: IMC-3G3; gastrointestinal stromal tumor; monoclonal antibody; mutation; platelet-derived growth factor receptor α.

Publication types

  • Clinical Trial, Phase II
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Aged
  • Antibodies, Monoclonal / administration & dosage*
  • Antibodies, Monoclonal / adverse effects
  • Cohort Studies
  • Disease-Free Survival
  • Drug-Related Side Effects and Adverse Reactions / pathology
  • Female
  • Gastrointestinal Stromal Tumors / drug therapy*
  • Gastrointestinal Stromal Tumors / genetics
  • Gastrointestinal Stromal Tumors / immunology
  • Gastrointestinal Stromal Tumors / pathology
  • Genotype
  • Humans
  • Kaplan-Meier Estimate
  • Male
  • Middle Aged
  • Mutation
  • Neoplasm Metastasis
  • Receptor, Platelet-Derived Growth Factor alpha / antagonists & inhibitors
  • Receptor, Platelet-Derived Growth Factor alpha / genetics*

Substances

  • Antibodies, Monoclonal
  • Receptor, Platelet-Derived Growth Factor alpha
  • olaratumab

Associated data

  • ClinicalTrials.gov/NCT01316263
  • ClinicalTrials.gov/NCT01316263