Phase I/II study of SAR439859, an oral selective estrogen receptor degrader (SERD), in estrogen receptor-positive (ER+)/human epidermal growth factor receptor 2-negative (HER2-) metastatic breast cancer (mBC).

Abstract No : 1070

Abstract Type : Poster Session (Board #155)

Indication : Her2-Negative Breast Cancer

Intervention : SAR439859

Company : Sanofi

Technology : SERD


Pts (n = 62; Part A, 13; Part B, 49) had a median age of 63 yrs (range 37–88) and ECOG PS 0 (59.7%) or 1 (40.3%); 93.5% had visceral disease. All had prior ET, 74.2% had prior targeted therapy and 48.4% had $ 3 prior lines in the advanced setting. 61.3% of pts had treatment-related adverse events (TRAEs), all grade 1–2. Most frequent: hot flush (16.1%), constipation, arthralgia (both 9.7%), decreased appetite, vomiting, diarrhea, nausea (all 8.1%), fatigue (6.5%). No pts discontinued due to AEs. CBR was 35.6% overall, with antitumor activity irrespective of ESR1 mutation status (Table). In pts with no prior SERD, CDK4/6 or mTOR inhibitors (n = 14), ORR was 21.4% and CBR 64.3%. PK data for Part B and ESR1 mutation data will be provided


SAR439859 had a favorable safety profile with limited TRAEs. In these heavily pre-treated pts (prior targeted therapy in 74.2%), ORR and CBR were similar to historical fulvestrant performance in pts with no prior targeted therapy. Encouraging ORR and CBR in pts with no prior SERD, CDK4/6 or mTOR inhibitors (n = 14; ORR 21.4%; CBR 64.3%) supports SAR439859 development in earlier lines of therapy.

Refer to Her2-Negative Breast Cancer Market report for detailed Insights.