Reduced Lymphodepletion With TILs Shows Promise in High-Risk Melanoma

A study demonstrates that tumor-infiltrating lymphocyte (TIL) therapy can be delivered safely and effectively to high-risk patients with metastatic melanoma using a reduced-dose lymphodepleting conditioning (LDC) regimen, a finding that could meaningfully expand eligibility for a treatment that can be inaccessible to patients with poor performance status, according to results published in Transplantation and Cellular Therapy.¹

The retrospective single-center analysis from Moffitt Cancer Center in Tampa, Florida, examined outcomes in 17 patients with advanced melanoma who received the commercially approved TIL product lifileucel (Amtagvi) preceded by a cyclophosphamide (Cy) dose halved from the standard 60 mg/kg/day to 30 mg/kg/day for 2 days, combined with the standard fludarabine (Flu) dose of 25 mg/m²/day for 5 days. Among 16 evaluable patients, the objective response rate (ORR) was 44%, broadly consistent with the pivotal trial data that supported the approval of lifileucel.

“Although the follow-up interval is short, we still saw responses,” said lead author Lilit Karapetyan, MD, in an interview with Targeted Oncology. “The objective response rate to therapy, which was around 44%, was truly encouraging, and it supports further development of this chemotherapy dose.”

Karapetyan, a medical oncologist at Moffitt Cancer Center and assistant professor at the University of South Florida Morsani College of Medicine, characterized the results as a meaningful step toward broadening access to cellular therapy, adding that the reduction in cyclophosphamide dose allowed completion of the full treatment course including at least 1 dose of IL-2 in every patient enrolled.

A High-Risk Patient Population

Lifileucel TIL therapy, which involves harvesting a patient’s own tumor-infiltrating immune cells, expanding them ex vivo, and reinfusing them following lymphodepletion, was approved by the FDA in February 2024 for unresectable or metastatic melanoma after prior therapy.² Although the TILs themselves are generally well tolerated, Karapetyan noted that the intensive conditioning regimen is substantially more aggressive than the Cy/Flu doses used in chimeric antigen receptor (CAR) T-cell therapy and has posed a significant barrier for older patients and those with comorbidities.

The Moffitt cohort reflects this underserved population.¹ Patients were eligible for the reduced-intensity protocol if they met 1 or more prespecified high-risk criteria: age 70 years or older, recently treated brain metastases, bowel metastases or bleeding history requiring surgical resection, recent deep vein thrombosis requiring anticoagulation, or coronary artery disease requiring recent percutaneous coronary intervention with continued antiplatelet therapy. The median patient age was 66 years (range, 36-78), 5 of 17 patients had brain metastases, and more than half had lactate dehydrogenase (LDH) levels above the upper limit of normal, indicating higher tumor burden. The median number of prior systemic therapies was 3.

“After approval of TIL therapy, it was critically important not to limit this therapy to exclusively fit patients, but truly expand access to more frail patients [and] older patients,” Karapetyan said.

Fewer Hematologic Toxicities Without Compromising Lymphodepletion

The standard Cy/Flu LDC regimen carries a well-characterized toxicity burden, including severe thrombocytopenia, febrile neutropenia, and prolonged neutropenia, all of which may preclude treatment in patients with limited physiologic reserve. The reduced regimen in this study appeared to attenuate these risks meaningfully. Grade 3 thrombocytopenia occurred in 47% of patients, whereas it occurred 77% in the pivotal C-144-01 trial (NCT02360579) and 89% in the Netherlands Cancer Institute (NKI) trial.^1,3,4 The incidence of febrile neutropenia was 59%, which was higher than in the C-144-01 trial but lower than the 86% reported in the NKI trial. The median duration of inpatient hospitalization was 14 days, whereas it was approximately 17 days in the NKI trial. No deaths occurred within 30 days of TIL infusion.

Importantly, despite the reduction in Cy dosing, all patients achieved the intended grade 4 lymphopenia, a prerequisite for adequate T-cell engraftment and the antitumor activity that follows. Neutrophil count recovery occurred at a median of 7 days, and platelet recovery at a median of 7 days, with 94% of patients recovering within 30 days of lymphodepletion.

Karapetyan highlighted the clinical significance of these hematologic findings in the context of the study’s patient population. The reduced regimen “was not associated with significant thrombocytopenia or prolonged neutropenia,” she noted, which “allowed it to be feasible to treat those high-risk patients.”

Among the cases described in the paper, 1 patient underwent a craniotomy between completion of LDC and TIL infusion, a surgery that would have been substantially riskier under standard conditioning. “We saw tremendous changes because we had this historical experience of taking care of patients with TIL…” Karapetyan said. “I think we certainly saw a huge difference in terms of management.”

IL-2 Tolerability and Inflammatory Marker Findings

All 17 patients received at least 1 dose of high-dose IL-2, with a median of 5 doses administered (range, 1-6). This is notable given that adequate IL-2 delivery of the maximum 6 doses can be compromised in patients with significant comorbidities. In the pivotal lifileucel trial, patients received a median of 6 doses; the reduced conditioning cohort, while receiving slightly fewer, demonstrated that even complex patients could tolerate meaningful IL-2 exposure.^1,3

“All of those patients were able to receive at least 1 dose of IL-2, which also speaks about [how] with adjustment of LDC, we are able to appropriately prepare the patient for subsequent cell infusion as well as high-dose IL-2.”

An exploratory analysis examined the relationship between baseline and post-infusion inflammatory markers C-reactive protein (CRP) and ferritin and treatment outcomes.¹ Baseline CRP levels correlated positively with tumor burden and with the incidence of grade 3 or higher treatment-emergent adverse events. Both CRP and ferritin levels rose significantly following TIL infusion, and higher post-infusion values were negatively correlated with the number of IL-2 doses patients received. These findings suggest that elevated inflammatory markers may serve as early warning signals for patients at risk of reduced IL-2 tolerability, potentially enabling more proactive dose modification.

Response Rates Comparable to Pivotal Trial

Among 16 RECIST-evaluable patients, 7 achieved a partial response (ORR, 44%), 3 had stable disease, and 6 had progressive disease. The ORR in patients with a BRAF mutation was 33% but was 50% in wild-type patients. The median duration of response had not been reached at a median follow-up of 10 months. The 12-month progression-free survival rate was 38%, and the 12-month overall survival rate was 61%. Of note, adverse events of autoimmune etiology, including uveitis, vitiligo, sensorineural hearing loss, and vertigo, occurred exclusively among responders, consistent with the known association between immune-related toxicity and treatment efficacy in TIL therapy.

The ORR with the reduced regimen is consistent with the 31.3% reported in heavily pretreated patients in historical trials and with the approximately 36% ORR seen in the pivotal lifileucel study, suggesting that halving the Cy dose did not meaningfully compromise antitumor activity.^1,3

Implications for Referral Practice and Future Research

These findings have given Karapetyan and others reassurance about treating older patients, provided they undergo proper workup and have good functional status. “Specifically for patients above 70, now we feel very comfortable treating those patients,” she said. “We do not consider [for] this treatment, that age is a strong limitation.”

Beyond the clinical data, the study carries important implications for how and when patients are referred for TIL therapy evaluation. Karapetyan has observed that community oncologists often delay referral, perceiving TIL therapy as prohibitively toxic, a hesitation that may inadvertently exclude patients who could benefit. “Because this therapy is preserved among other providers as more of a ‘toxic’ therapy, providers choose to refer patients late when they exhausted prior lines of therapies.” Real-world data from Moffitt have shown that patients with fewer prior therapy lines, normal LDH, and lower-stage disease (M1a) have the highest response rates, which she said is suggestive that earlier referral is critical to optimizing outcomes.⁵

“Once the patient progresses through first-line combination immunotherapy, patients should be referred for evaluation of TIL therapy,” Karapetyan recommended. This applies even to patients who might appear to be poor candidates based on age or comorbidity profile, given the demonstrated feasibility of dose-adjusted conditioning.

She said she has already shared these findings with patients to offer them a more tolerable treatment path. “Now we expand this to other patients as well. We talk to them about these data, and hopefully we can continue using this approach and follow on a long-term duration of the response and truly confirm this is more suitable regimen for TIL therapy conditioning.”

Looking ahead, the group plans to move toward prospective validation of the reduced-intensity approach, including investigation of strategies that combine immunotherapy with LDC to potentially reduce conditioning further or eliminate systemic chemotherapy altogether in favor of outpatient-compatible regimens comparable to those used in CAR T-cell therapy. Questions around IL-2 dose optimization are also under active investigation, with an eye toward identifying patients who may safely receive fewer doses without sacrificing efficacy.

The current data, although limited by sample size and follow-up duration, represent a real-world demonstration that lifileucel can be administered safely to high-risk patients with melanoma through objective risk-stratified dose reduction, and that doing so need not come at the cost of meaningful clinical response.

REFERENCES

1. Karapetyan L, Kuriakose J, DiMaggio E, et al. Safety and efficacy of tumor-infiltrating lymphocyte therapy with reduced-dose lymphodepleting conditioning in high-risk metastatic melanoma patients. Transplant Cell Ther. 2026;32:290.e1-290.e14. doi:10.1016/j.jtct.2025.12.009

2. FDA approves first cellular therapy to treat patients with unresectable or metastatic melanoma. FDA. February 16, 2024. Accessed March 31, 2026. https://tinyurl.com/53832kzh

3. Chesney J, Lewis KD, Kluger H, et al. Efficacy and safety of lifileucel, a one-time autologous tumor-infiltrating lymphocyte (TIL) cell therapy, in patients with advanced melanoma after progression on immune checkpoint inhibitors and targeted therapies: pooled analysis of consecutive cohorts of the C-144-01 study. J Immunother Cancer. 2022;10(12):e005755. doi:10.1136/jitc-2022-005755

4. Rohaan MW, Borch TH, van den Berg JH, et al. Tumor-infiltrating lymphocyte therapy or ipilimumab in advanced melanoma. N Engl J Med. 2022;387(23):2113-2125. doi:10.1056/NEJMoa2210233

5. Karapetyan L, Moser J, Ma BT, et al. Real-world, evidence-based, retrospective study of patients infused with commercially released lifileucel for unresectable or metastatic melanoma. Presented at: 2026 Transplantation & Cellular Therapy Meetings. February 4-7, 2026. Salt Lake City, Utah. Abstract 48.