Merck & Co. Inc. (NYSE:MRK) and healthcare company Daiichi Sankyo voluntarily pulled their U.S. Biologics License Application (BLA) seeking accelerated approval for a new lung cancer treatment.
The partners sought clearance for ifinatamab deruxtecan (I-DXd). The drug is meant to treat adults with extensive-stage small cell lung cancer (ES-SCLC) that progressed after platinum-based chemotherapy.
FDA Discussions Prompt Withdrawal
The companies made this decision following conversations with the U.S. Food and Drug Administration (FDA).
The agency indicated that the current application data fails to satisfy the requirements for the accelerated approval pathway.
In September 2025, the companies shared response rates from the phase 2 IDeate-Lung01 trial. A confirmed objective response rate (ORR) of 48.2% was observed with ifinatamab deruxtecan in 137 patients with previously treated ES-SCLC.
Three complete responses (CRs), 63 partial responses (PRs), and 54 cases of stable disease (SD) were seen. A median duration of response (DOR) of 5.3 months and a disease control rate (DCR) of 87.6% were observed.
Median progression-free survival (PFS) was 4.9 months, and median overall survival (OS) was 10.3 months. Disease progression and time-to-event results support further randomized, controlled assessment.
In a subset of patients (n=32) receiving ifinatamab deruxtecan as a second-line treatment, a confirmed ORR of 56.3% was observed.
Eighteen PRs and 13 cases of SD were seen in this subset of patients. The median DOR was 7.2 months, and the DCR was 96.9%. The median PFS was 5.6 months, and the median OS was 12.0 months.
In a subset of patients (n=105) receiving ifinatamab deruxtecan in a third-line and beyond setting, a confirmed ORR of 45.7% was observed, with three CRs, 45 PRs, and 41 cases of SD. These patients had a DCR of 84.8%.
The company observed an intracranial ORR of 46.2% d in a subset of patients (n=65) with brain metastases at baseline.
Ongoing Phase 3 Trials Continue
Despite the BLA withdrawal, the phase 3 IDeate-Lung02 trial continues to enroll patients, comparing I-DXd against standard physician-chosen chemotherapy options for relapsed ES-SCLC.
Daiichi Sankyo originally discovered I-DXd, a targeted antibody-drug conjugate, and now jointly develops the therapy with Merck.
The two companies also continue to actively evaluate the treatment in two additional phase 3 studies targeting advanced prostate and esophageal cancers.
Licensing Pact
Concurrently, on Monday, Merck announced an exclusive global license agreement with SciBrunch Therapeutics Co., Ltd. for SPR2015, an investigational preclinical oral KRAS G12D (ON) inhibitor.
Under the agreement, SciBrunch will receive an upfront payment of $400 million and is eligible to receive milestone payments. The total potential aggregate value of the transaction, including the upfront payment, is $2.13 billion.
Merck will record a pre-tax charge of $400 million, or about 13 cents per share, in the third quarter of 2026.
MRK Price Action: Merck shares were down 0.08% to $148.66 at the time of publication on Monday, according to Benzinga Pro data.
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