In order to treat relapsed estrogen receptor (ER)-positive ovarian cancer (OC) and endometrial cancer (EC), the researchers provide the details of phase II clinical trial of the mix of ribociclib and letrozole. With 45% or more thought to be positive, the key endpoint was the extent of patients who were still living, progression-free survival (PFS) and even now receiving treatment at 12 weeks (PFS12).

To be eligible, patients needed to have quantifiable, relapsed ER-positive OC or EC (either sensitive to platinum or resistance). Those eligible patients were given 400 milligrams of oral ribociclib and 2.5 milligrams of oral letrozole every day as treatment. Imaging-guided tumor biopsies were used to produce patient-derived xenografts (PDXs).


20 patients with OC and 20 patients with EC were signed up for the second phase of a clinical trial. In the group of patients with EC, a PFS12 of 55% was noted whilst a PFS12 of 50% was noted in the group of patients with OC. About 20% (4/20) of the patients with OC were found to have a PFS greater than or equal to 24 weeks (PFS24) while a PFS24 was noted in 35% (7/20) of the patients with EC. The best advantage was found in low-grade serous OC (LGSOC) (3/3, 100% PFS24) and grades 1 and 2 EC (5/11, 45% PFS24). Each of the three LGSOC patients had received at least a partial response that went on for over 2 years, with two of them still on treatment. It was easy to do PDX tumor engraftment in 45% of the patients. Out of the three EC PDX models, two showed improved survival effects of the mixture of ribociclib and letrozole. A favorable clinical activity can be expected from ribociclib and letrozole in relapsed ER-positive OC and EC, especially in relapsed ER-positive grade 1 and 2 EC and in LGSOC. PDX models can be generated with positive survival effects noted in EC models.