What Is Tarlatamab (Imdelltra)? FDA Approval, Licensing and Reimbursement in Türkiye
| Active ingredient | Tarlatamab-dlle (intravenous) |
| Brand name | Imdelltra |
| Class | DLL3–CD3 bispecific T-cell engager (BiTE) |
| Category | Immunotherapy / antineoplastic agent |
| Administration | Intravenous (IV) infusion — over 1 hour |
| Frequency | After a three-step dose-escalation schedule, every 2 weeks |
| Approved cancer | Following progression after platinum-based chemotherapy: extensive-stage small cell lung cancer (ES-SCLC) |
| FDA approved | Yes — accelerated approval May 16, 2024; full approval November 19, 2025 |
| Frequently used concomitant drugs | Dexamethasone (premedication to prevent CRS) · tocilizumab (CRS treatment) |
| Manufacturer | Amgen Inc. |
| Licensing by Türkiye's Ministry of Health | NONE |
| SGK reimbursement | NONE |
| Access in Türkiye | Only through overseas medicine procurement (with TİTCK approval, patient-funded) |
| Half-life | Approximately 11 days |
Tarlatamabis changing the treatment approach to small cell lung cancer (SCLC). For decades, the standard was cytotoxic chemotherapy , drugs that directly poison tumor cells. Tarlatamab takes a different approach: rather than targeting the tumor directly, it directs your immune system's own T cells toward it.
This monograph explains how the drug works, its FDA approval history, including the transition from accelerated to full approval in November 2025 , phase 3 DeLLphi-304 findings, dosing, safety, and access in Türkiye.
DLL3 (Delta-like ligand 3) is a protein almost absent from healthy tissues but highly expressed on small cell lung cancer cells. CD3 is a receptor complex on T lymphocytes, the immune system's “soldier” cells.
Tarlatamab is bispecific : one arm binds DLL3 and the other CD3, physically bringing the T cell close to the tumor cell and activating your own immune system to kill cancer. This is entirely different from conventional chemotherapy.
- Bispecific structure: Produced by recombinant DNA technology in Chinese hamster ovary (CHO) cells, it contains 982 amino acids and has a molecular weight of approximately 105 kilodaltons.
- Selectivity: DLL3 is expressed only minimally in healthy lung and other tissues but abundantly in most SCLC cells, making treatment relatively tumor-selective.
- Cytokine release: T-cell activation temporarily releases IL-2, IL-6, IL-8, IL-10, and IFN-γ. This is also the biological basis of cytokine release syndrome (CRS), the drug's most frequent adverse reaction and one requiring particular attention.
- Dose–response relationship: No efficacy difference has been demonstrated between 10 mg and 100 mg (10 times the approved dose), but neutropenia and neurologic toxicity increase at higher doses. The dose therefore does not exceed 10 mg.
| Date | Approval Details | Supporting Evidence |
|---|---|---|
| October 20, 2023 | Amgen presented phase 2 tarlatamab findings in SCLC. | DeLLphi-301 |
| December 13, 2023 | The FDA accepted the advanced SCLC application for Priority Review . | — |
| May 16, 2024 | For second-line extensive-stage SCLC after platinum therapy: accelerated approval. | DeLLphi-301 (accelerated approval) |
| April 11, 2025 | The phase 3 trial met its primary overall survival (OS) endpoint at the planned interim analysis. | DeLLphi-304 |
| June 2, 2025 | Primary analysis findings were presented at ASCO and simultaneously published in NEJM. | DeLLphi-304 |
| November 19, 2025 | Accelerated approval became full approval ; NCCN guidelines updated tarlatamab as the sole Category 1 preferred agent for this indication. | DeLLphi-304 (phase 3, randomized) |
Full approval rests not on single-arm phase 2 findings, but on the randomized controlled phase 3 DeLLphi-304 trial. This moved the evidence from a response-rate-based hypothesis to a causal survival benefit.
509 patients with progression after platinum-based chemotherapy (± anti-PD-(L)1) were randomized 1:1 to tarlatamab or investigator-selected standard chemotherapy (topotecan, lurbinectedin, or amrubicin). At a median 11–12 months of follow-up, median overall survival was 13.6 months with tarlatamab, compared with 8.3 months with standard chemotherapy (HR 0.60; 95% CI 0.47–0.77; p<0.001).
| Study | Population | Comparison | Main Result |
|---|---|---|---|
| DeLLphi-304 phase 3 · n=509 |
ES-SCLC progressing after platinum | Tarlatamab vs standard chemotherapy (topotecan/lurbinectedin/amrubicin) | OS advantage: 13.6 vs 8.3 months (HR 0.60; p<0.001). PFS advantage: 4.2 vs 3.2 months (HR 0.72; p<0.001). OS rates at 6/12 months: 76%/53% vs 62%/37%. Significant patient-reported improvements in dyspnea and cough. |
| DeLLphi-301 phase 2 · n=99 |
Relapsed/refractory SCLC after at least two treatment lines | Single-arm | Objective response rate 40%; median response duration 9.7 months. Basis for accelerated approval in 2024. |
| DeLLphi-300 phase 1 |
SCLC, various treatment lines | Dose escalation / expansion | Foundational safety and dose-selection findings (10 mg); included in the pooled safety population. |
Similar survival benefit was observed in patients with a short chemotherapy-free interval (<90 days; HR 0.60) and those with a longer interval (HR 0.65), suggesting that tarlatamab may also be effective in platinum-resistant disease .
Sudden, intense T-cell activation can trigger substantial cytokine release (CRS). To limit this, treatment starts at a very low dose and reaches the target dose in three steps ; the full 2-week dosing interval begins only from the second cycle.
- After Cycle 1 Day 1 and Day 8 doses, patients are advised, from the start of infusion, to remain for a total of 48 hours with a caregiver, within 1 hour of an appropriate healthcare facility .
- If a dose is delayed, the step-up schedule may need to be repeated in full or in part, depending on the delay.
- Routine dose reduction is not recommended; dose modifications consist only of delay or permanent discontinuation.
- Check a complete blood count, liver enzymes, and bilirubin before every dose through Cycle 5 Day 15, then on the first day of each cycle from Cycle 6 onward.
Absorption: Intravenous administration provides direct 100% bioavailability. Exposure increases linearly with dose across 1–100 mg.
Distribution: As a monoclonal-antibody-derived protein, it remains largely in vascular/interstitial spaces. Steady-state volume of distribution is 8.5 L. Steady state is reached on Cycle 2 Day 15.
Metabolism: Not metabolized by hepatic CYP450 enzymes; catabolic pathways break it down into small peptides.
Elimination: Terminal elimination half-life: 11 days; estimated systemic clearance: 0.7 L/day. No significant differences were observed by mild/moderate kidney impairment, mild liver impairment, age, body weight, sex, or race.
| Parameter | First step-up dose (1 mg) | First treatment dose (10 mg) | Steady state (10 mg every 2 weeks) |
|---|---|---|---|
| Cavg, ng/mL | 106 | 1100 | 1040 |
| Cmax, ng/mL | 314 | 3190 | 3640 |
| Ctrough, ng/mL | 49 | 517 | 472 |
Antidrug antibodies (ADAs) developed in 8% of patients (36/445) during treatment. ADA development was associated with an average 14% increase in clearance, but its clinical effect remains uncertain because of the small number of cases.
- Tarlatamab itself is not metabolized by CYP450 enzymes, but the transient cytokine release it triggers may suppress them.
- During and after CRS, this may, for up to 14 days, increase plasma levels of concurrently administered CYP-substrate drugs, including certain anticoagulants, anticonvulsants, and immunosuppressants.
- Close clinical/laboratory monitoring is recommended for patients taking drugs with a narrow therapeutic index.
- Through the immune system: Corticosteroids and other immunosuppressants may theoretically reduce tarlatamab efficacy by suppressing T-cell activity. However, corticosteroids are necessary to manage CRS/ICANS, and treatment must not be delayed in these situations.
- Premedication: Dexamethasone and IV fluids on Cycle 1 Day 1 and Day 8 aim to reduce CRS risk, rather than address a pharmacokinetic interaction.
- Other T-cell activators / IL-2-like agents: Concurrent use may synergistically increase CRS and neurotoxicity risk; clinical data are limited.
- Cytokine release syndrome (CRS): 57% (39% Grade 1, 15% Grade 2, 1.7% Grade 3, 0.2% Grade 4). Most frequent after the first two doses.
- Neurologic toxicity (including ICANS): Any grade 65% (Grade ≥3: 7%); most commonly dysgeusia, headache, peripheral neuropathy, dizziness, and insomnia. ICANS-specific findings in 10%.
- Cytopenias: Neutropenia 16% (Grade 3/4: 9%), thrombocytopenia 30% (Grade 3/4: 2.2%), anemia 56% (Grade 3/4: 4.7%).
- Infections: 43% (Grade 3/4: 14%); most commonly pneumonia, urinary tract infection, and COVID-19.
- Hepatotoxicity: ALT 39%, AST 43%, bilirubin 16% (Grade 3/4: 2.5%/3.2%/1.3%, respectively).
- General: Fatigue (48%), reduced appetite (38%), fever (33%), constipation (31%), musculoskeletal pain (31%), nausea (25%).
- CRS management: For Grade ≥2: hospitalization, cardiac telemetry, and, when needed, tocilizumab (or equivalent) ± dexamethasone; for Grade 3–4, intensive care assessment, with permanent discontinuation for recurrent Grade 3/4 events.
- ICANS monitoring: Grade using the ICE score (ASTCT 2019); Grade ≥2 requires dexamethasone/methylprednisolone, neurology consultation, and neuroimaging when needed. ICANS may arise weeks after treatment (median onset: 16 days after the first dose).
- Driving and Operating Machinery: Patients developing dizziness, confusion, tremor, or drowsiness should avoid driving or operating machinery until symptoms resolve.
- Pregnancy and Breastfeeding: During treatment and for 2 months after the final dose, effective contraception is recommended; breastfeeding is not recommended for the same period.
- No contraindications have been reported; dose reduction is not recommended: management uses delay or permanent discontinuation only.
Loss of DLL3 expression, T-cell exhaustion from chronic antigen stimulation, and an immunosuppressive tumor microenvironment (Tregs, M2 macrophages, PD-L1 enrichment) are mechanistic hypotheses thought to contribute to resistance. They are based on preclinical observations and limited clinical sample series. They are not formally defined as a “resistance profile” in FDA prescribing information, and no biomarker approach has been validated sufficiently to change clinical practice.
Licensing: Imdelltra, containing tarlatamab-dlle, is not licensed by Türkiye's Ministry of Health; there is no registered license information in the TİTCK database.
Reimbursement: Not reimbursed by SGK.
Consequently: The drug is not marketed in Türkiye. When needed, it must be obtained from abroad , generally through a physician's request, patient consent, and TİTCK approval.
- Physician application. The treating medical oncologist documents the diagnosis, stage, and previous treatments and applies through the TİTCK procedure.
- Patient consent. The process begins with patient consent; its experimental/unapproved status and potential risks are discussed with the patient.
- TİTCK assessment and approval. TİTCK reviews the application. If approved, importation is authorized through the overseas medicine procurement pathway.
- Procurement and cost. The drug is generally imported, and because SGK does not cover its cost, the patient pays.
The process is governed by regulations and may change over time. Consult the appropriate department of the treating center about current procedures.
Who Is This Drug For? Patients with extensive-stage small cell lung cancer progressing after platinum-based chemotherapy.
How Is It Given? By an intravenous infusion lasting approximately 1 hour. The first two doses require 22–24 hours of observation in a healthcare facility, followed by staying nearby with a caregiver for the next 48 hours as a precaution against cytokine release syndrome (CRS).
What Should You Watch For? Immediately report fever, chills, a rapid heartbeat, shortness of breath, dizziness, or altered awareness such as forgetfulness, speech problems, or imbalance. These symptoms can also appear days or weeks later.
How Is It Obtained in Türkiye? Because it is not licensed in Türkiye, access depends on your physician's application and TİTCK approval through overseas medicine procurement, at the patient's expense. Your treating oncologist initiates this process.
Tarlatamab offers, against the decades-long cytotoxic chemotherapy standard in SCLC, an immune-mediated alternative . As the first approved DLL3-targeted bispecific T-cell engager, its transition in November 2025 to full approval supported by randomized phase 3 evidence shows that it has established a new second-line standard in SCLC.
DeLLphi-304 (n=509): Tarlatamab improves overall survival versus standard chemotherapy: HR 0.60 (95% CI 0.47–0.77; p<0.001), median OS 13.6 vs 8.3 months. A PFS advantage was also demonstrated (4.2 vs 3.2 months; HR 0.72). Benefit was similar in platinum-resistant and nonresistant disease. DeLLphi-301 (n=99): In the single-arm phase 2 study, response rate was 40% and median response duration 9.7 months. Safety is predictable: CRS 57% (mostly Grade 1–2), neurologic toxicity 65% (only 7% Grade ≥3).
DeLLphi-304 is open-label, which matters when interpreting patient-reported endpoints. Patients with symptomatic brain metastases were excluded. CRS and neurotoxicity risk require close monitoring and hospitalization for initial doses , increasing access and logistical burdens. Resistance mechanisms remain mechanistic hypotheses and have not been formally defined. The most decisive limitation in Türkiye is that the drug is neither licensed nor reimbursed.
Safe administration of tarlatamab is limited to centers equipped to manage CRS and ICANS , with cardiac telemetry, ICU access, and tocilizumab availability as prerequisites. Strict adherence to step-up dosing and premedication is the main way to reduce severe CRS risk. In Türkiye, decisions are often determined, even before efficacy, by access to an appropriate center and the overseas procurement process .
DeLLphi-303 (first-line combination) and DeLLphi-305 (durvalumab combination) will determine whether tarlatamab moves beyond second-line treatment. What treatments should follow resistance? Which patients benefit most, and can a predictive biomarker be found? For Türkiye, the most practical question is: when will licensing and reimbursement progress?
- This document provides no dose-adjustment advice and recommends no treatment regimen.
- The drug is neither licensed nor reimbursed in Türkiye; FDA approval does not mean access.
- DeLLphi-304 survival benefits must be weighed against CRS and neurotoxicity risk.
- Resistance mechanisms remain mechanistic hypotheses; no formal resistance profile has been defined.
- Treatment decisions belong solely to the medical oncologist who knows the patient.
- IMDELLTRA (tarlatamab-dlle) Prescribing Information, Amgen Inc., revised 11/2025. FDA access: accessdata.fda.gov (761344s001lbl).
- Mountzios G, Sun L, Cho BC, et al. Tarlatamab in Small-Cell Lung Cancer after Platinum-Based Chemotherapy (DeLLphi-304). N Engl J Med. 2025;393(4):349-361.
- Ahn MJ, Cho BC, Felip E, et al. Tarlatamab for Patients with Previously Treated Small-Cell Lung Cancer (DeLLphi-301). N Engl J Med. 2023;389(22):2063-2075.
- Amgen Inc. FDA Grants Full Approval to IMDELLTRA in Extensive Stage Small Cell Lung Cancer. Press release, November 19, 2025.
- Rudin CM, Mountzios GS, Sun L, et al. Primary analysis of Phase 3 DeLLphi-304 (2L SCLC). Presented at: ASCO Annual Meeting, 2025 (LBA8008).
- NCCN Clinical Practice Guidelines in Oncology: Small Cell Lung Cancer, Version 2.2026.
Editor's note: This monograph is for general information only; it is not medical advice, a diagnosis, or a treatment recommendation, and does not promote any product. All reported data were verified against primary sources and paraphrased without direct quotation. This document intentionally contains no dose-adjustment advice; dosing information is summarized from FDA prescribing information solely for general education, and treatment decisions remain the treating physician's responsibility. Tarlatamab is not licensed by Türkiye's Ministry of Health or reimbursed by SGK; FDA approval does not mean a drug is licensed, accessible, or reimbursed in Türkiye. Overseas procurement is governed by regulations and may change over time. DeLLphi-304 survival benefits must be considered alongside cytokine release syndrome and neurotoxicity risks; treatment selection depends not only on efficacy but also on the patient's general condition, comorbidities, and the center's ability to manage CRS/ICANS. Reported resistance mechanisms remain mechanistic hypotheses and have not been validated sufficiently to change clinical practice. Do not stop or change any medicine without consulting your physician. For procurement, consult only your treating medical oncologist. Consult a physician who knows you about every health decision.
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