(Breast Cancer) Is Patritumab Deruxtecan Effective?

From June 3–7, 2022, Dr. Ian E. Krop and colleagues from the Dana-Farber Cancer Institute presented results at the American Society of Clinical Oncology (ASCO) annual meeting in Chicago on the efficacy and safety of patritumab deruxtecan in the U31402-A-J101 Phase 1/2 clinical trial in previously treated HER3-positive metastatic breast cancer patients.

The U31402-A-J101 Phase 1/2 trial was an open-label, multi-center study. An initial dose-escalation phase enrolled 66 patients with HER3-positive metastatic breast cancer and evaluated the safety, tolerability, and maximum tolerated dose of patritumab deruxtecan on a 3-week cycle. Subsequent dose-expansion cohorts enrolled different patient subtypes at the following doses:

• HER3 high-expressing group: 4.8 mg/kg (N=66) and 6.4 mg/kg (N=31)
• HER3 low-expressing group: 6.4 mg/kg (N=21)
• HR+/HER2−, triple-negative, and HER3 high-expressing: 6.4 mg/kg (N=31)

Patient characteristics: median age 57 years (range: 30–83), ECOG PS 0 in 72.5% (N=132) and ECOG PS 1 in 27.5% (N=50), median prior therapies: 5 (range: 1–13).

At a median follow-up of 31.9 months, objective response rates (ORR) were:

• HR+/HER2−, HER3 high+low expressing: 30.1% (N=113)
• Triple-negative breast cancer, HER3 high-expressing: 22.6% (N=53)
• HER2-positive, HER3 high-expressing: 42.9% (N=14)

Median duration of response was:

• HR+/HER2−, HER3 high+low expressing: 7.2 months
• Triple-negative, HER3 high-expressing: 5.9 months
• HER2-positive, HER3 high-expressing: 8.3 months

Safety: Grade 3 or higher adverse events occurred in 71.4% (N=130). Adverse events occurring in ≥15% of patients included: neutropenia (39.6%), thrombocytopenia (30.8%), anemia (18.7%), and leukopenia (18.1%). Treatment-related interstitial lung disease was observed in 6.6% (N=12), including one Grade 5 event.

Conclusion: Based on U31402-A-J101 trial results, Dr. Krop and colleagues concluded that patritumab deruxtecan demonstrated meaningful anti-tumor activity with manageable tolerability in previously treated HER3-positive metastatic breast cancer patients across triple-negative, HR+/HER2−, and HER2-positive subtypes.

Source: https://meetings.asco.org/abstracts-presentations/206936

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