Extended-Interval Tarlatamab Dosing Offers Pharmacists More Flexible Administration Windows in SCLC

Pharmacists managing infusion schedules for small cell lung cancer (SCLC) may soon have more room to work with. Results from the randomized phase 2 DeLLphi-309 study (NCT06745323) show that less frequent dosing of the bispecific T-cell engager tarlatamab (Imdelltra; Amgen, Inc) can maintain efficacy, safety, and pharmacokinetic profiles broadly consistent with its established every-2-week schedule.¹

The data were presented at the International Association for the Study of Lung Cancer (IASLC) 2026 World Conference on Lung Cancer (WCLC) in Seoul, South Korea.

“I am appreciative that clinical studies are both discovering treatments that create a significant clinical impact in patients’ lives and also formulating strategies that allow the treatments themselves to be more patient-centered,” said Andrew Li, PharmD, BCOP, a clinical oncology pharmacist at Providence Regional Medical Center Everett-Colby Campus in Everett, Washington. “The feasibility of extending an every-2-week treatment cycle to an every-3-week or every-4-week interval is certainly an endeavor worth examining, as that option can make a meaningful quality-of-life improvement for patients.”

What Did the DeLLphi-309 Study Evaluate?

Tarlatamab 10 mg every 2 weeks previously demonstrated superior overall survival (OS) compared with chemotherapy in previously treated SCLC in the Phase 3 DeLLphi-304 trial.² DeLLphi-309 evaluated whether 20 mg every 3 weeks or 30 mg every 4 weeks could match that activity while easing the treatment burden on patients and infusion centers.³ Adults whose SCLC progressed after platinum-based chemotherapy were randomized to 1 of the 3 intravenous regimens, each preceded by a 1-mg step dose.

The primary end point was confirmed objective response rate (ORR) by blinded independent central review (BICR); no formal statistical hypotheses were prespecified, and results were reported descriptively.¹

How Did the Extended-Interval Regimens Perform?

As of the data cutoff on May 7, 2026, 252 patients were randomly assigned to a treatment group. BICR-confirmed ORR was approximately 40% with the every-2-week regimen, 31% with every-3-week dosing, and 27% with every-4-week dosing. Median progression-free survival rates by BICR were about 4.2, 4.1, and 2.7 months, respectively. Six-month OS rates were 72%, 85%, and 69%, respectively'; however, median OS had not yet been reached after roughly 9 months of follow-up.

“These data suggest that the tarlatamab 20 mg every-3-week and 30 mg every-4-week regimens may offer treatment flexibility for patients with SCLC,” said Jonathan Goldman, MD, of the University of California Los Angeles, who presented the findings.¹

What Does the Safety Data Show?

Treatment-emergent and treatment-related adverse event rates were similar across all 3 regimens, with no new or unexpected signals. But cytokine release syndrome (CRS) and immune effector cell-associated neurotoxicity syndrome (ICANS) were numerically higher with extended-interval dosing. CRS occurred in 60% to 70% of patients, predominantly grade 1 or 2, and ICANS in 6% to 12%. Steady-state trough concentrations were comparable across all 3 schedules.¹

“While the excitement is valid for a prospect that can be this impactful, it must be weighed with a degree of caution,” Li explained. “The safety data signaled that the extended intervals had higher rates of CRS and ICANS than the standard regimen.

“Without the reported numbers yet, however, it is difficult to evaluate the difference of safety across the different regimens. Although the every-3-week and every-4-week intervals’ outcomes appeared numerically similar to the standard regimen's, the absence of statistical analysis adds a degree of uncertainty when it comes to comparing the efficacy outcomes,” he said. “In addition, this dataset only reports 6-month OS rates, while the original landmark trial DeLLphi-304 reports a more robust dataset of 12-month OS rates.”

What Should Pharmacists Take Away From These Findings?

Fewer infusion visits could ease scheduling strain and give patients more flexibility to balance treatment with daily life. But the higher CRS and ICANS rates in the extended-interval arms suggest premedication protocols and monitoring windows may need revisiting rather than simply stretching to fit the new schedule.

Since no formal statistical comparisons were prespecified, these results are best read as hypothesis-generating rather than practice-changing on their own.

“Overall, with the data as it is currently reported, providers and pharmacists alike may be open to exploring and utilizing the extended intervals but would likely appreciate additional data or analysis that is released,” said Li. “This is an encouraging finding, as it allows additional flexibility to those patients in need, especially for those with transportation difficulties or access challenges.”

REFERENCES

1. Goldman J, et al. Extended-interval dosing regimens of tarlatamab in previously treated small cell lung cancer: results from the randomized Phase 2 DeLLphi-309 study. Presented at: IASLC 2026 World Conference on Lung Cancer; September 12, 2026; Seoul, Republic of Korea.

2. Mountzios G, Sun L, Cho BC, et al. Tarlatamab in small-cell lung cancer after platinum-based chemotherapy. N Engl J Med. 2025;393:349-361. doi:10.1056/NEJMoa2502099

3. A phase 2, open-label, randomized, multicenter study of tarlatamab dosing regimens in subjects with small cell lung cancer (DeLLphi-309). ClinicalTrials.gov identifier: NCT06745323. Updated August 17, 2026. Accessed September 8, 2026. https://clinicaltrials.gov/study/NCT06745323