Managing Tarlatamab Toxicity: A Practical Guide for Oncology Pharmacists

Tarlatamab (Imdelltra; Amgen), a first-in-class bispecific T-cell engager (BiTE) targeting delta-like ligand 3 (DLL3) on tumor cells and CD3 on T cells, received accelerated FDA approval in May 2024 for adult patients with extensive-stage small cell lung cancer (ES-SCLC) who progressed on or after platinum-based chemotherapy.^1ˌ2 It is the first T-cell engager approved for SCLC—and it brings a toxicity profile that is mechanistically distinct from chemotherapy or checkpoint inhibitors.

Pharmacists who understand the timing, grading, and management of tarlatamab’s key adverse events will be better positioned to keep patients on therapy safely and for longer.

What Are the Boxed Warnings For Tarlatamab, and What Do They Mean in Practice?

The tarlatamab prescribing information carries 2 boxed warnings: cytokine release syndrome (CRS) and neurologic toxicity, including immune effector cell-associated neurotoxicity syndrome (ICANS), both of which can be life-threatening or fatal.² These are class effects of T-cell engaging immunotherapies and reflect the mechanism—T-cell activation triggers inflammatory cytokine release that can affect multiple organ systems.

The practical implication for pharmacists is that tarlatamab cannot be treated like a conventional cytotoxic: it requires structured premedication, step-up dosing, mandatory post-infusion monitoring, and institutional readiness with tocilizumab (Actemra; Genentech) on hand before the first dose is administered.²

How Does the Step-Up Dosing Schedule Work, and Why Does It Matter?

Step-up dosing is the central CRS mitigation strategy for tarlatamab. In the DeLLphi-301 trial (NCT05060016), patients received a 1 mg primer dose on cycle 1 day 1, followed by the full 10 mg dose on cycle 1 days 8 and 15, then 10 mg every 2 weeks from cycle 2 onward.³ The low initial dose gradually primes the immune system and reduces the risk and severity of CRS by avoiding an abrupt full-dose immune activation.

Pharmacists verifying tarlatamab orders should confirm that the 1 mg step-up dose is correctly prescribed for cycle 1, day 1. This is a pharmacist-catchable dosing error with meaningful clinical consequences if missed. If treatment is interrupted, restart guidelines defined in the protocol apply depending on the reason for interruption.³

What Is the CRS Profile With Tarlatamab, and When Should Pharmacists Expect It?

CRS occurred in 70 of 133 patients (53%) in the DeLLphi-301 trial, but the severity profile is reassuring: 60% of events were grade 1 and 39% were grade 2; only one patient (1.4%) experienced grade 3 CRS, and there were no grade 4 or 5 events.³ The median time to CRS onset from the first dose was 13.7 hours (IQR, 9.3–33.2 hours), meaning CRS typically emerges within the first day of each infusion—which is why hospitalization after cycle 1, day 1, and 8 doses, is required.³ Fever (97% of CRS events) is the defining symptom; hypotension occurred in 20% and hypoxia in 16% of patients who experienced CRS.³ Recurrent CRS occurred in 25% of patients but was predominantly grade 1 and concentrated in cycle 1.³

What Premedications Are Required, and What Must Be Available On Site?

Two prophylactic strategies are mandated in the DeLLphi-301 protocol and should be standard practice: dexamethasone 8 mg IV (or equivalent) within 1 hour before the cycle 1 day 1 and day 8 doses and 1 liter of normal saline IV over 4 to 5 hours immediately after all cycle 1 doses.³ The rationale is direct—corticosteroids reduce CRS incidence and severity, and IV hydration offsets the hypotensive effects that can escalate CRS grade.³ Critically, clinical trial sites were required to have tocilizumab (or siltuximab as an alternative) available on site before administering tarlatamab.³

Pharmacists should verify formulary availability of tocilizumab and confirm that at least 2 doses are accessible before the first infusion. For grade 2 CRS, tocilizumab 8 mg/kg IV over 1 hour (not exceeding 800 mg) is recommended, repeatable every 8 hours as needed up to 4 doses total.³

What Is ICANS With Tarlatamab, and How Is it Different From CRS?

ICANS occurred in 13 of 133 patients (10%) in DeLLphi-301, with all events being grade 1 (54%) or grade 2 (46%)—no grade 3 or higher events were observed.³ Unlike CRS, which peaks within hours of infusion, ICANS onset is delayed: the median time to the first ICANS event was 30 days from the first tarlatamab dose (IQR, 13–47 days).³

Symptoms included confusion, impaired attention, motor weakness, dysgraphia, and increased tone.³ ICANS is a diagnosis of exclusion—symptoms can mimic infection, stroke, CNS disease progression, electrolyte disturbances, and medication side effects, all of which must be ruled out before attributing neurologic symptoms to tarlatamab.³ Grade 1 is managed with supportive care; grade 2, with dexamethasone 10 mg IV or methylprednisolone 1 mg/kg IV; grade 3 or higher requires ICU-level care, interruption for at least 3 days, and potential permanent discontinuation.³

What Other Toxicities Should Pharmacists Track Over the Longer Treatment Course?

Three additional toxicities deserve structured monitoring beyond the early CRS/ICANS window. Dysgeusia occurred in 32% of patients with a median onset of 34 days; it is hypothesized to reflect DLL3-mediated T-cell destruction of DLL3-expressing taste bud cells.³ No pharmacologic management is established, but nutritional counseling, adequate hydration, and oral hygiene measures can help patients manage it.

Neutropenia occurred in 16% of patients with a median onset of 56 days—notably delayed compared to CRS—and febrile neutropenia in less than 1%.³ G-CSF is permitted for grade 3 neutropenia; dose interruption is indicated for grade 3 until improvement to grade 2 or lower, and discontinuation is considered for grade 4 or unremitting grade 3.³

Liver enzyme elevations (ALT increase in 11.3%, AST increase in 10.5%) were generally transient and did not result in treatment discontinuation in DeLLphi-301, but baseline and pre-dose LFT monitoring is required.³

What Does the Post-Infusion Monitoring Schedule Look Like, and How Should Pharmacy Teams Prepare?

Monitoring requirements are intensive during cycle 1 and taper with experience. Hospitalization is required after cycle 1 days 1 and 8, with 48-hour observation per the standard DeLLphi-301 protocol (a 24-hour reduced hospitalization substudy showed a generally similar safety profile).³ Cycle 1, day 15, requires 6–8 hours of monitoring if the patient had no CRS or neurologic events on earlier doses; prior events extend the monitoring requirement. From cycle 2 onward, monitoring duration decreases stepwise.³

After discharge, patients must remain within 1 hour of travel from the site for 48 hours and within 1 hour of a hospital for 72 hours after cycle 1 day 1 and day 8 doses and must have a home companion.³ Pharmacy teams should coordinate early morning infusion scheduling—starting infusions as early as possible maximizes daytime monitoring by the main shift and reduces overnight coverage gaps.³

REFERENCES

1. FDA grants accelerated approval to tarlatamab-dlle for extensive stage small cell lung cancer. News release. FDA. Published May 16, 2024. Accessed August 13, 2026. https://www.fda.gov/drugs/resources-information-approved-drugs/fda-grants-accelerated-approval-tarlatamab-dlle-extensive-stage-small-cell-lung-cancer

2. Amgen Inc. IMDELLTRA (tarlatamab-dlle) [prescribing information]. Thousand Oaks, CA: Amgen Inc.; 2024. https://www.accessdata.fda.gov/drugsatfda_docs/label/2024/761344s000lbl.pdf

3. Sands JM, Champiat S, Hummel H-D, et al. Practical management of adverse events in patients receiving tarlatamab, a delta-like ligand 3–targeted bispecific T-cell engager immunotherapy, for previously treated small cell lung cancer. Cancer. 2025;e35738. doi:10.1002/cncr.35738