Merck & Co.'s Keytruda significantly improves pathological complete response rates in patients with triple-negative breast cancer

Merck & Co. said Monday that in a Phase III trial, Keytruda (pembrolizumab) in combination with chemotherapy demonstrated a significant improvement in pathological complete response (pCR) rates compared with chemotherapy alone in patients with triple-negative breast cancer (TNBC). The company noted that Keytruda is the first anti-PD-1 therapy to achieve this result as a neoadjuvant treatment for TNBC regardless of PD-L1 status.

Roger Perlmutter, president of Merck Research Laboratories, remarked "we are encouraged by these results and plan to discuss these data with health authorities and to present these findings at an upcoming medical congress." The drugmaker said that based on the recommendation of the independent Data Monitoring Committee, the KEYNOTE-522 trial will continue without changes to evaluate the other dual-primary endpoint of event-free survival (EFS).  

In the study, 1174 patients with TNBC were randomly assigned to treatment with Keytruda or placebo, both in combination with chemotherapy, as neoadjuvant therapy prior to surgery, with subjects subsequently treated with nine cycles of Keytruda or placebo after surgery. In addition to the primary endpoints of pCR, defined as the absence of all signs of cancer in tissue samples analysed after neoadjuvant therapy and definitive surgery, and EFS, secondary goals included pCR rate using alternative definitions at the time of definitive surgery, EFS in patients with PD-L1-positive tumours and overall survival (OS).  

The results come after Merck announced in May that Keytruda failed to prolong OS versus chemotherapy in patients with second- or third-line metastatic TNBC in the Phase III KEYNOTE-119 trial. The company is conducting two other registration-enabling studies in TNBC, namely KEYNOTE-355 and KEYNOTE-242.  

Keytruda, which is currently approved for a number of tumour types, including melanoma, non-small-cell lung cancer and renal cell carcinoma, generated sales of $2.3 billion in the first quarter, a 55% increase year-on-year (for additional analysis, read ViewPoints: Key takeaways from Merck & Co.'s Q1 earnings and investor call).

For related analysis, see ViewPoints: Keytruda steps back into the breast cancer ring.

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