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O22 - Mesothelioma III (ID 122)
- Event: WCLC 2013
- Type: Oral Abstract Session
- Track: Mesothelioma
- Presentations: 1
O22.05 - Exposure-response Relationship of Amatuximab (AMA) in Combination with Pemetrexed and Cisplatin (P/C) in Patients with Unresectable Pleural Mesothelioma (ID 1609)
16:15 - 17:45 | Author(s): A. Gupta
AMA is chimeric monoclonal antibody that binds to mesothelin, which is highly expressed in malignant mesothelioma and largely absent from normal tissue. In vitro studies indicate that AMA potentially has anti-tumor activity via antibody-dependent cellular cytotoxicity. AMA was studied in a Phase 2 mesothelioma trial.
This was a global, single arm, open label Phase 2 trial in 89 patients with previously untreated epithelial or mixed histology unresectable malignant pleural mesothelioma. Subjects received P/C every three weeks for 4 to 6 cycles combined with AMA 5mg/kg on days 1 and 8 of each 21 day cycle. All patients were fully supplemented with folate and B12 as per pemetrexed label requirements. Single agent AMA was then continued in the same schedule until disease progression. The primary endpoint was progression-free survival (PFS) at 6 months with a secondary end point of overall survival (OS).
Median PFS was 6.1 months while median OS was 14.8 months. An evaluation of serum drug concentration relationship with clinical response noted that those subjects who achieved a median trough serum concentration of 32.9 µg/mL had an improved median PFS over those whose trough serum concentration was below the median (238 days vs 115 days, p<0.001). Similarly those subjects with a serum trough concentration of AMA above a median of 38.2 µg /mL had a median OS of 583 days while those with a median serum concentration of AMA below 38.2 µg /mL had a median OS of 375 days, p=0.0202. The most commonly reported adverse event was that of hypersensitivity to the chimeric antibody at first dose second cycle.
The safety profile of AMA in combination with P/C was consistent with that seen previously for the PC regimen. Although PFS is not significantly different from historical results of P/C alone, the median OS was 14.8 months (as compared to 13.3 months for P/C). PK/PD analysis demonstrated that AMA trough concentrations were a significant predictor of both PFS and OS where higher concentrations were associated with longer OS and PFS. Reference: Vogelzang NJ, Rusthoven JJ, Symanowski J, et al. Phase III Study of Pemetrexed in Combination With Cisplatin Versus Cisplatin Alone in Patients With Malignant Pleural Mesothelioma. J Clin Oncol, 2003; 21:2636-2644.
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