A B S T R A C T PurposeTo evaluate the safety and efficacy of IMC-A12, a human monoclonal antibody (mAb) that blocks insulin-like growth factor receptor-1 (IGF-1R), as monotherapy or in combination with cetuximab in patients with metastatic refractory anti-epidermal growth factor receptor (EGFR) mAb colorectal cancer.
MethodsA randomized, phase II study was performed in which patients in arm A received IMC-A12 10 mg/kg intravenously (IV) every 2 weeks, while patients in arm B received this same dose of IMC-A12 plus cetuximab 500 mg/m 2 IV every 2 weeks. Subsequently, arm C (same combination treatment as arm B) was added to include patients who had disease control on a prior anti-EGFR mAb and wild-type KRAS tumors. Archived pretreatment tumor tissue was obtained when possible for KRAS, PIK3CA, and BRAF genotyping, and immunohistochemistry was obtained for pAKT as well as IGF-1R.
ResultsOverall, 64 patients were treated (median age, 61 years; range, 40 to 84 years): 23 patients in arm A, 21 in arm B, and 20 in arm C. No antitumor activity was seen in the 23 patients treated with IMC-A12 monotherapy. Of the 21 patients randomly assigned to IMC-A12 plus cetuximab, one patient (with KRAS wild type) achieved a partial response, with disease control lasting 6.5 months. Arm C (all patients with KRAS wild type), however, showed no additional antitumor activity. Serious adverse events thought possibly related to IMC-A12 included a grade 2 infusion-related reaction (2%; one of 64 patients), thrombocytopenia (2%; one of 64 patients), grade 3 hyperglycemia (2%; one of 64 patients), and grade 1 pyrexia (2%, one of 64 patients).
ConclusionIMC-A12 alone or in combination with cetuximab was insufficient to warrant additional study in patients with colorectal cancer refractory to EGFR inhibitors.
Olaratumab was well tolerated and showed preliminary antitumor activity. RP2Ds are 16 mg/kg weekly and 20 mg/kg biweekly. Phase II studies of olaratumab as monotherapy and in combination are ongoing in several tumor types.
Olaratumab (IMC-3G3) is a fully human IgG1 monoclonal antibody that selectively binds the external domain of human platelet-derived growth factor receptor-α with high affinity and blocks ligand binding. This was a single-center, dose-escalation, phase I trial of olaratumab in Japanese patients with advanced/refractory solid malignancies. Three to six patients were enrolled into each of three cohorts: Patients received i.v. olaratumab: 10 mg/kg on days 1 and 8 every 3 weeks (cohort 1); 20 mg/kg every 2 weeks (cohort 2); and 15 mg/kg on days 1 and 8 every 3 weeks (cohort 3). Doses were escalated from cohort 1 through cohort 3. The primary objective was to establish the safety and pharmacokinetic profile of olaratumab. Sixteen patients were treated across three cohorts. There were no dose-limiting toxicities, so the maximum tolerated dose was not reached. The most common olaratumab-related treatment-emergent adverse events (TEAEs) were proteinuria (25.0%) and elevated aspartate transaminase (12.5%). One patient (cohort 2) had two olaratumab-related Grade 3 TEAEs (increased aspartate aminotransferase and tumor hemorrhage); otherwise, olaratumab-related TEAEs were Grade 1/2. Seven patients (43.8%) had a best response of stable disease. Based on the pharmacokinetic concentration profile of olaratumab, the trough concentrations following single and multiple doses at 15 mg/kg on days 1 and 8 every 3 weeks (cohort 3) and multiple doses at 20 mg/kg every 2 weeks (cohort 2) were above the 155 μg/mL target. Thus, these two doses could represent an acceptable schedule for future trials in Japanese patients. Olaratumab had an acceptable safety profile and was well tolerated.
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