FDA Reduces Monitoring Time for First Two Tarlatamab Doses

The FDA approved an update to the tarlatamab (Imdelltra; Amgen) prescribing information that sharply cuts the post-infusion monitoring period for the first 2 doses, a change that could make the bispecific T-cell engager far more practical to administer outside large academic centers.

Patients beginning therapy now require 6 to 8 hours of monitoring from the start of each of the first 2 infusions, down from the 22 to 24 hours previously recommended, easing a logistical barrier that has kept much of the initial treatment tied to inpatient or extended-observation settings.¹

What Changed in the Label

The revision applies specifically to the Cycle 1 Day 1 and Cycle 1 Day 8 doses, which now call for 6 to 8 hours of observation in an appropriate health care setting rather than roughly a full day.

The update also adds a follow-up assessment, including a vital signs check, the day after each of those 2 doses—on Cycle 1 Days 2 and 9. Tarlatamab is indicated for adults with extensive-stage small cell lung cancer (ES-SCLC) whose disease has progressed on or after platinum-based chemotherapy, an aggressive setting in which most patients relapse within months of first-line therapy.¹

The Rest of the Schedule Is Unchanged

Beyond the first 2 doses, the monitoring and supportive care recommendations hold steady. Patients are still observed for 6 to 8 hours after the third dose (Cycle 1 Day 15) and throughout Cycle 2, dropping to 3 to 4 hours for Cycles 3 and 4 and 2 hours from Cycle 5 onward.

Following the Day 1 and Day 8 infusions, patients should remain within 1 hour of an appropriate health care setting for a total of 48 hours, accompanied by a caregiver—a point pharmacists can reinforce when confirming a patient's support plan before the first dose.^1-3

Safety Still Anchors the Protocol

The monitoring requirements are crucial because tarlatamab carries a boxed warning for cytokine release syndrome (CRS) and neurologic toxicity, including immune effector cell-associated neurotoxicity syndrome (ICANS).

In the pooled safety population, CRS occurred in 57% of treated patients and neurologic toxicity in 65%, and most CRS events clustered around the earliest doses. The median time to onset of all-grade CRS was 16 hours from the most recent dose, which is why the drug is initiated with step-up dosing and premedication.^1,3

Notably, ICANS can emerge well after the infusion—its median time to onset was 16 days, with cases reported as late as more than 2 years out—so the shorter in-clinic window does not lessen the need for ongoing vigilance and clear return-precaution counseling. Before discharge, both the patient and caregiver should be counseled on the signs and symptoms of CRS and ICANS, and complete blood counts, liver enzymes, and bilirubin should be evaluated ahead of each dose through Cycle 5 Day 15.^1,3

What It Means for Community Practice

The change is aimed squarely at access. An estimated 80% to 85% of patients with cancer in the US receive care in community oncology practices, where a 22- to 24-hour monitoring window can be difficult to accommodate. By trimming that window for the initial doses, the update may let more patients begin tarlatamab closer to home rather than traveling to a tertiary center.²

The approval follows Amgen's recent report of positive topline overall survival data from the phase 3 DeLLphi-305 trial evaluating tarlatamab with Imfinzi (durvalumab; AstraZeneca) in first-line ES-SCLC, part of a broader effort to expand where and how the therapy can be used, and it may also simplify scheduling and chair-time planning for pharmacy and infusion teams.^1,2

REFERENCES

1. FDA approves reduced monitoring time for first two doses of IMDELLTRA. News release. Amgen. Released September 14, 2026. Accessed September 17, 2026. https://www.amgen.com/newsroom/press-releases/2026/09/fda-approves-reduced-monitoring-time-for-first-two-doses-of-imdelltra

2. Birhiray RE, Birhiray MN. Clinical research in the community. Hematology Am Soc Hematol Educ Program. 2023;2023(1):324-331. doi:10.1182/hematology.2023000432

3. IMDELLTRA (tarlatamab-dlle) prescribing information. Amgen Inc.; 2026. Accessed September 17, 2026. https://www.pi.amgen.com/united_states/Imdelltra/imdelltra_fpi.pdf