On 7 April, Merck & Co. and Tokyo-based Eisai provided an update on the Phase lll trials LEAP-003 and LEAP-017 which evaluate the combination of Merck’s Keytruda (pembrolizumab) with Eisai’s Lenvima (lenvatinib) as a first-line treatment in patients with metastatic melanoma and relapsed/refractory colorectal cancer, respectively.

The first trial (LEAP 003) was discontinued after an independent data monitoring committee found that the combination failed to improve overall survival (OS), which was one of the study’s dual endpoints, along with progression-free survival (PFS).

The second trial (LEAP-017) evaluates the drug cocktail for relapsed colorectal patients whose disease is mismatch repair proficient (pMMR) or not microsatellite instability-high (MSI-H) against Bayer‘s targeted therapy Stivarga (regorafenib) or Taiho Oncology’s chemotherapy Lonsurf (TAS-102). It has yet to exhibit statistically significant OS, but the results have been positive; therefore, the study will continue. The combination of PD1 checkpoint inhibitor Keytruda with small-molecule kinase inhibitor Lenvima is approved for advanced renal cell carcinoma, as well as various types of advanced endometrial carcinoma.

Merck & Co. and Eisai began the collaboration in 2015, naming it the LEAP program and testing this drug combination in multiple solid tumour indications. While the drug combination received approval in 2021 for endometrial and advanced kidney cancers, its success has been underwhelming. Failures of the drug combination included newly diagnosed non-small cell lung cancer (NSCLC) and bladder cancer, where Keytruda monotherapy showed better OS than the combination, as well as newly diagnosed liver cancer, where the combination could not demonstrate statistically significant OS versus Lenvima alone.

Lenvima is approved for liver, thyroid, and kidney cancer and had sales of $2.2bn in 2022, accounting for roughly 30% of Japanese pharma’s total global revenue. Eisai’s reliance on the drug to generate earnings can be tempered with the January approval of its Alzheimer’s medication Leqembi (lecanemab), which is projected to earn $8.5bn a year by 2029, according to GlobalData’s analyst consensus forecast. Sales of Merck’s Keytruda, which is one of the top-selling drugs in the world, skyrocketed to $20.9bn in 2022, up 27% year-over-year. Its projected yearly sales are expected to reach $34bn by 2028 when it comes off patent.

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Despite the latest setback for the Keytruda + Lenvima combination, the companies are forging ahead with several LEAP trials in various tumour types, including melanoma, NSCLC, head and neck cancer, and others. Time is of the essence for Lenvima to gain more approvals, as its patent is set to expire in 2026.