FDA Grants Priority Review to BLA for Ifinatamab Deruxtecan in Pretreated ES-SCLC

A biologics license application (BLA) seeking the approval of ifinatamab deruxtecan (I-DXd) for the treatment of adult patients with extensive-stage small cell lung cancer (ES-SCLC) with disease progression on or after platinum-based chemotherapy has been accepted and granted priority review by the FDA.¹

The BLA is informed by data from the phase 2 IDeate-Lung01 trial (NCT05280470), with support from the phase 1/2 IDeate-PanTumor01 trial (NCT04145622). Findings from the primary analysis of IDeate-Lung01 published in the Journal of Clinical Oncology demonstrated that patients with ES-SCLC who received I-DXd at 12 mg/kg (n = 137) experienced a confirmed overall response rate (ORR) of 48.2% (95% CI, 39.6%-56.9%).² The median duration of response (DOR), time to response (TTR), and progression-free survival (PFS) were 5.3 months (95% CI, 4.0-6.5), 1.4 months (range, 1.0-8.1), and 4.9 months (95% CI, 4.2-5.5), respectively. The estimated 9-month overall survival (OS) rate was 59.1% (95% CI, 50.4%-66.8%).

“The FDA’s granting of priority review for [I-DXd] marks a significant milestone in our effort to provide new and innovative treatment options for patients with [ES-SCLC],” John Tsai, MD, the global head of R&D at Daiichi Sankyo, stated in a news release.¹ “We look forward to continuing to work with the FDA to bring this potential first-in-class, B7-H3–directed DXd antibody-drug conjugate to patients as quickly as possible.”

How was IDeate-Lung01 designed?

The first-in-human IDeate-Lung01 trial enrolled adult patients with histologically or cytologically confirmed ES-SCLC who previously received at least 1 line of platinum-based chemotherapy and no more than 3 lines of systemic therapy, and experienced radiologically documented disease progression on or after the most recent systemic regimen.² Patients were also required to have at least 1 measurable lesion per RECIST 1.1 criteria, an ECOG performance status of 0 or 1, and adequate organ function. During part 2 enrollment, the study protocol was amended to require 2 to 3 prior lines of systemic therapy.

In part 1, patients were randomly assigned 1:1 to receive intravenous I-DXd at 8 mg/kg or 12 mg/kg every 3 weeks until unacceptable toxicity, disease progression, or patient withdrawal. In part 2, all patients were treated with I-DXd at 12 mg/kg every 3 weeks.

The primary end point was ORR per blinded independent central review by RECIST 1.1 criteria. Secondary end points included DOR, disease control rate, TTR, PFS, OS, safety, and pharmacokinetic measures.

What were the additional efficacy and safety data from IDeate-Lung01?

Further data from IDeate-Lung01 revealed that patients treated at the 8-mg/kg (n = 46) and 12-mg/kg (n = 42) dose levels in part 1 achieved ORRs of 26.1% (95% CI, 14.3%-41.1%) and 54.8% (95% CI, 38.7%-70.2%), respectively. The respective median TTR values were 1.4 months (95% CI, 1.3-2.6) and 1.4 months (95% CI, 1.0-8.1); the median DOR values were 7.9 months (95% CI, 4.1-not evaluable) and 4.2 months (95% CI, 3.5-7.0), respectively.

Patients in the safety population who received I-DXd at 12 mg/kg (n = 137) experienced any-grade treatment-emergent adverse effects (TEAEs) at a rate of 98.5%. Grade 3 TEAEs (62.0%), serious TEAEs (39.4%), as well as TEAEs associated with dose interruption (1.5%), dose delay (35.8%), dose reduction (17.5%), treatment discontinuation (10.9%), and death (11.7%) were reported. The most common any-grade TEAEs that were reported in more than 10% of patients included nausea (48.2%), anemia (45.3%), decreased appetite (38.7%), and neutropenia (38.0%).

“SCLC remains one of the toughest cancers to treat, with few options if the disease progresses after standard-of-care treatments,” Eliav Barr, MD, senior vice president, head of global clinical development, and chief medical officer at Merck Research Laboratories, added in the news release.¹ “The FDA’s acceptance of the BLA reinforces the important role that [I-DXd] could play in helping to address the needs of patients with [ES-SCLC].”

References

1. Ifinatamab deruxtecan granted priority review in the U.S. for adult patients with previously treated extensive-stage small cell lung cancer who experienced disease progression on or after platinum-based chemotherapy. News release. Daiichi-Sankyo. April 13, 2026. Accessed April 13, 2026. https://daiichisankyo.us/web/dsi/press-releases/-/article/ifinatamab-deruxtecan-granted-priority-review-in-the-us-for-adult-patients-with-previously-treated-extensive-stage-small-cell-lung-cancer-who-experienced-disease-progression-on-or-after-platinum-based-chemotherapy
2. Rudin CM, Johnson ML, Paz-Ares L, et al. Ifinatamab deruxtecan in patients with extensive-stage small cell lung cancer: primary analysis of the phase II IDeate-Lung01 Trial. J Clin Oncol. 2026;44(4):261-273. doi:10.1200/JCO-25-02142