A randomized phase II trial of ridaforolimus, dalotuzumab, and exemestane compared with ridaforolimus and exemestane in patients with advanced breast cancer.

PURPOSE: To evaluate whether adding humanized monoclonal insulin growth factor-1 receptor (IGF-1R) antibody (dalotuzumab) to mammalian target of rapamycin (mTOR) inhibitor (ridaforolimus) plus aromatase inhibitor (exemestane) improves outcomes in patients with estrogen receptor (ER)-positive advanced/metastatic breast cancer. METHODS: This randomized, open-label, phase II trial enrolled 80 postmenopausal women with high-proliferation (Ki67 index staining ≥15%), ER-positive breast cancer that progressed after a non-steroidal aromatase inhibitor (NCT01605396). Randomly assigned patients were given oral ridaforolimus 10 mg QD 5 ×/week, intravenous dalotuzumab 10 mg/kg/week, and oral exemestane 25 mg/day (R/D/E, n = 40), or ridaforolimus 30 mg QD 5 ×/week and exemestane 25 mg/day (R/E; n = 40). Primary end point was progression-free survival (PFS). RESULTS: Median PFS was 23.3 weeks for R/D/E versus 31.9 weeks for R/E (hazard ratio 1.18; 80% CI 0.81-1.72; P = 0.565). Grade 3-5 adverse events were reported in 67.5% of patients in the R/E arm and 59.0% in the R/D/E arm. Stomatitis (95.0 vs. 76.9%; P = 0.021) and pneumonitis (22.5 vs. 5.1%; P = 0.027) occurred more frequently in the R/E than the R/D/E arm; hyperglycemia (27.5 vs. 28.2%) occurred at a similar rate. CONCLUSIONS: R/D/E did not improve PFS compared with R/E. Because the PFS reported for R/E was similar to that reported for everolimus plus exemestane in patients with advanced breast cancer, it is possible that lower-dose ridaforolimus in the R/D/E arm (from overlapping toxicities with IGF1R inhibitor) contributed to lack of improved PFS.

A phase II study of combined ridaforolimus and dalotuzumab compared with exemestane in patients with estrogen receptor-positive breast cancer.

PURPOSE: Combining the mTOR inhibitor ridaforolimus and the anti-IGFR antibody dalotuzumab demonstrated antitumor activity, including partial responses, in estrogen receptor (ER)-positive advanced breast cancer, especially in high proliferation tumors (Ki67 > 15%). METHODS: This randomized, multicenter, international, phase II study enrolled postmenopausal women with advanced ER-positive breast cancer previously treated with a nonsteroidal aromatase inhibitor (NCT01234857). Patients were randomized to either oral ridaforolimus 30 mg daily for 5 of 7 days (once daily [qd] × 5 days/week) plus intravenous dalotuzumab 10 mg/kg/week or oral exemestane 25 mg/day, and stratified by Ki67 status. Due to a high incidence of stomatitis in the ridaforolimus-dalotuzumab group, two sequential, nonrandomized, reduced-dose cohorts were explored with ridaforolimus 20 and 10 mg qd × 5 days/week. The primary endpoint was progression-free survival (PFS). RESULTS: Median PFS was 21.4 weeks for ridaforolimus 30 mg qd × 5 days/week plus dalotuzumab 10 mg/kg (n = 29) and 24.3 weeks for exemestane (n = 33; hazard ratio = 1.00; P = 0.5). Overall survival and objective response rates were similar between treatment arms. The incidence of drug-related, nonserious, and serious adverse events was higher with ridaforolimus/dalotuzumab (any ridaforolimus dose) than with exemestane. Lowering the ridaforolimus dose reduced the incidence of grade 3 stomatitis, but overall toxicity remained higher than acceptable at all doses without improved efficacy. CONCLUSIONS: The combination of ridaforolimus plus dalotuzumab was no more effective than exemestane in patients with advanced ER-positive breast cancer, and the incidence of adverse events was higher. Therefore, the combination is not being further pursued.