Merck’s Keytruda hits the mark in triple negative breast cancer

Merck’s star PD-1 inhibitor Keytruda has demonstrated promising results in the first-line treatment of patients with metastatic triple negative breast cancer (TNBC), making it a likely rival to Roche’s TNBC treatment Tecentriq.

Pivotal phase 3 data, revealed at the virtual ASCO 2020 meeting, showed that Keytruda (pembrolizumab) in combination with chemotherapy reduced the risk of death by 35% in previously untreated metastatic TNBC patients whose tumours expressed high levels of PD-L1.

In this patient group, the Keytruda treatment also improved progression-free survival (PFS), with those receiving the drug reaching a median of 9.7 months compared to 5.6 months for those who received chemotherapy alone.

For patients whose tumours expressed lower levels of PD-L1, the Keytruda plus chemotherapy regimen improved PFS compared to chemotherapy alone, but the results did not meet statistical significance. The trial is on track to evaluate the primary endpoint of overall survival, with no changes being made to the study in the meantime.

Roche’s Tecentriq (atezolizumab) is the undisputed leader in the TNBC market, having won the first immunotherapy approval in this indication last March. It is approved in combination with chemotherapy (Celgene’s Abraxane, nab-paclitaxel) as a treatment for adults with metastatic TNBC whose tumours express PD-L1, the same patient population that Merck is angling for.

Until now, Roche has had the TNBC market largely to itself, and as a result the Swiss pharma company has estimated that the indication could be worth up to $1bn in additional revenues for Tecentriq.

Merck is eager to crack the market, with two additional studies of Keytruda in TNBC aiming to expand the potential clinical profile of the PD-1 inhibitor in the disease. That includes a study in early-stage TNBC patients, comparing Keytruda chemotherapy given before and after surgery to try to prevent recurrence.

The second trial, which is sponsored by the National Cancer Institute (NCI), is testing adjuvant use (post-surgery) of the immunotherapy following initial chemotherapy treatment.

Merck also revealed some new data at ASCO for Keytruda in the treatment of adult patients with relapsed or refractory classical Hodgkin lymphoma (cHL). The PD-1 inhibitor demonstrated statistically significant improvement in PFS by a media of 13.2 months compared to 8.3 months for patients treated with the current standard of care treatment brentuximab vedotin (BV).

Keytruda remains dominant in the anti-PD-1/L1 category, with EvaluatePharma forecasting that sales of the drug will reach $24.3bn in 2026. Merck has lined up a number of trials of the drug in a host of cancer types, although much of its dominance is thanks to its ongoing leading position in the non-small cell lung cancer (NSCLC) market.