Phase 1 dose-escalation study of mirvetuximab soravtansine (IMGN853), a folate receptor α-targeting antibody-drug conjugate, in patients with solid tumors

BACKGROUND

Mirvetuximab soravtansine (IMGN853) is an antibody-drug conjugate that selectively targets folate receptor α (FRα). In this phase 1 dose-escalation study, the authors investigated IMGN853 in patients with FRα-positive solid tumors.

METHODS

Patients received IMGN853 on day 1 of a 21-day cycle (once every 3 weeks dosing), with cycles repeated until patients experienced dose-limiting toxicity or progression. Dose escalation commenced in single-patient cohorts for the first 4 planned dose levels and then followed a standard 3 + 3 scheme. The primary objectives were to determine the maximum tolerated dose and the recommended phase 2 dose. Secondary objectives were to determine safety and tolerability, to characterize the pharmacokinetic profile, and to describe preliminary clinical activity.

RESULTS

In total, 44 patients received treatment at doses escalating from 0.15 to 7.0 mg/kg. No meaningful drug accumulation was observed with the dosing regimen of once every 3 weeks. The most common treatment-related adverse events were fatigue, blurred vision, and diarrhea, the majority of which were grade 1 or 2. The dose-limiting toxicities observed were grade 3 hypophosphatemia (5.0 mg/kg) and grade 3 punctate keratitis (7.0 mg/kg). Two patients, both of whom were individuals with epithelial ovarian cancer, achieved confirmed tumor responses according to Response Evaluation Criteria in Solid Tumors 1.1, and each was a partial response.

CONCLUSIONS

IMGN853 demonstrated a manageable safety profile and encouraging preliminary clinical activity, particularly in patients with ovarian cancer. The results establish a recommended phase 2 dosing of 6.0 mg/kg (based on adjusted ideal body weight) once every 3 weeks. Cancer 2017. © 2017 American Cancer Society.

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