Eisai today announced updated results of ENHANCE 1, a Phase 1b/2 trial investigating eribulin mesylate, in combination with pembrolizumab, in patients with metastatic triple-negative breast cancer .

Findings presented during the 2017 San Antonio Breast Cancer Symposium (SABCS) showed the combination of eribulin and pembrolizumab resulted in an objective response rate (ORR) of 26.4% (95% CI: 18.3 – 35.9), the primary efficacy endpoint of the study.

Three complete responses were observed; one of which was in a patient with a PD-L1–negative tumour.

Treatment-emergent adverse events (TEAEs) for the combination regimen were comparable to those observed with each treatment as a monotherapy.

Eribulin and pembrolizumab are not approved for use in combination.

“The results observed, namely the response rates and tolerability achieved with the eribulin and pembrolizumab combination regimen, broaden our knowledge base as to the possible effect of these two agents when used together in patients with metastatic TNBC,” said Sara Tolaney, MD, MPH, medical oncologist, Dana-Farber Cancer Institute, Boston, and the principal investigator of the study.

“The potential of the combination of eribulin plus pembrolizumab for this aggressive form of breast cancer is exciting for both patients and physicians alike.”

The combination of eribulin and pembrolizumab demonstrated activity in patients with mTNBC regardless of PD-L1 status or prior treatment with chemotherapy.

In the evaluable analysis set (n=106), patients who were PD-L1-positive (n=49) had an ORR of 30.6% and patients who were PD-L1-negative (n=49) had an ORR of 22.4%.

Patients with mTNBC who had no prior chemotherapy treatment in the metastatic setting (n=65) had an ORR of 29.2% (95% CI: 18.6 – 41.8) and patients who received one or two prior lines of chemotherapy (n=41) had an ORR of 22.0% (95% CI: 10.6 – 37.6).1 The median duration of response was 8.3 months (6.5 – 12.9) and the response lasted longer than six months in 53.6% of responders.

The clinical benefit rate (CBR, complete response partial response durable stable disease [duration greater than or equal to 24 weeks]) was 36.8%.

Median overall survival and median progression-free survival for all patients in the trial (the full analysis set; n=107), both secondary endpoints, were 17.7 months (95% CI: 13.7 – not estimable) and 4.2 months (95% CI: 4.1 – 5.6), respectively.1

The most common treatment-emergent adverse events (TEAEs) for the combination regimen were fatigue, peripheral neuropathy, nausea, alopecia, and constipation.

The most common grade 3 or 4 TEAEs for the combination regimen were neutropaenia, peripheral neuropathy, and anaemia, fatigue, and hypokalaemia.

Dose reduction due to TEAEs occurred in 32% of patients.

Drug withdrawal due to TEAEs occurred in 22% of patients.1

“Most of the major advances in breast cancer treatment to date have been for patients whose cancers express the receptors currently identified as targets for treatment; limited options exist for patients with metastatic triple-negative breast cancer,” said Alton Kremer, MD, PhD, Chief Clinical Officer and Chief Medical Officer, Oncology Business Group at Eisai.

“These updated results give us confidence to continue to study eribulin in the treatment of metastatic breast cancer in combination with new agents, like checkpoint inhibitors. We are very encouraged by the activity seen when adding pembrolizumab to eribulin, and we are eager to further assess these data and their meaning for patients with metastatic TNBC.”

Source: SABCS 2017