Citation
Strong J, Miller DM, Brownell I. Tumor-infiltrating lymphocyte therapy receives FDA approval. Journal of Cutaneous Oncology. 2024;2(1). doi:10.59449/joco.2024.05.01.
Why this approval matters
Immune checkpoint inhibitors transformed advanced melanoma, but primary and acquired resistance remain common. For patients whose disease progresses after anti–PD-1 therapy, treatment options are limited and often provide modest response rates.
Lifileucel introduces a fundamentally different strategy: rather than further intensifying checkpoint inhibition, tumor-reactive lymphocytes are harvested from the patient’s own tumor, expanded outside the body, and reinfused after lymphodepleting chemotherapy.
The approval of lifileucel is a landmark for melanoma and for solid-tumor cellular therapy. Its clinical value, however, will depend not only on response probability but also on manufacturing time, treatment intensity, center capacity, tumor accessibility, cost, and the ability to identify patients healthy enough to reach infusion.
How TIL therapy works
Tumor harvest
A surgically accessible tumor is removed and used as the source of naturally occurring tumor-reactive lymphocytes.
Ex vivo expansion
The lymphocytes are isolated and expanded into a personalized cellular product containing billions of viable cells.
Lymphodepletion
Cyclophosphamide and fludarabine are used before infusion to create an immune environment that supports cellular engraftment.
Cell infusion and IL-2
Lifileucel is infused once, followed by interleukin-2 to support expansion and persistence of the transferred lymphocytes.
The regulatory evidence at a glance
Patients in the BLA efficacy set
All had advanced melanoma previously treated with anti–PD-1 therapy and, when appropriate, BRAF-targeted therapy.
Investigator-assessed ORR
The cohort included three complete responses and 20 partial responses.
Responses generally emerged early
Clinical benefit was often evident within the first several weeks after infusion.
Among responders
A meaningful subset of responses persisted for at least one year.
Why accelerated approval was granted
The FDA granted accelerated approval on February 16, 2024, based on objective response rate and duration of response in a population with substantial unmet need. The label covers adults with unresectable or metastatic melanoma previously treated with anti–PD-1 therapy and, for patients with a BRAF V600 mutation, a BRAF inhibitor with or without a MEK inhibitor.
As with other accelerated approvals, continued authorization depends on confirmation of clinical benefit in a required postmarketing trial.
Lifileucel was approved because the magnitude and durability of tumor responses were judged reasonably likely to predict clinical benefit—not because a randomized trial had already demonstrated an improvement in survival.
The treatment burden
- Nearly all patients experience substantial treatment-related toxicity.
- Lymphodepleting chemotherapy can cause prolonged cytopenias, infection, bleeding, and organ dysfunction.
- Interleukin-2 can produce hemodynamic, pulmonary, renal, and constitutional toxicity.
- Patients require treatment at specialized centers with intensive supportive-care capability.
- The process is best viewed as a one-time cellular-treatment episode rather than a conventional outpatient infusion.
Manufacturing and access
Centralized production
Tumor is shipped to a manufacturing facility, where the individualized cellular product is generated.
Approved collection centers
Access was initially concentrated at academic hospitals able to perform harvest, bridging care, and infusion.
Projected patients per year
Manufacturing scale remains limited relative to the potential population with checkpoint-refractory melanoma.
Single-treatment acquisition cost
This does not include surgery, hospitalization, lymphodepletion, interleukin-2, or supportive care.
Where lifileucel may fit
- Patients progressing after combination checkpoint inhibition who remain fit enough for intensive cellular therapy.
- Patients without an actionable BRAF mutation who need a second-line strategy after anti–PD-1–based treatment.
- Patients with accessible tumor tissue and disease tempo slow enough to permit manufacturing.
- Patients without a more attractive clinical-trial option.
- Patients who understand the tradeoff between a one-time intensive treatment and a possibility of durable response.
Why sequencing remains unsettled
For BRAF-mutant disease, the label generally positions lifileucel after both anti–PD-1 therapy and BRAF-directed treatment. For BRAF-wild-type disease, clinicians must choose among ipilimumab plus nivolumab, nivolumab plus relatlimab, lifileucel, and clinical trials.
Response rates with lifileucel are broadly comparable to dual checkpoint blockade in the PD-1–refractory setting, but the tradeoffs differ. Combination immunotherapy is faster to initiate and more widely available; lifileucel may offer a one-time treatment with the potential for durable control but requires tumor harvest, manufacturing, hospitalization, and greater logistical coordination.
Lifileucel is unlikely to replace every second-line option. Its strongest role may be in patients who are fit, have accessible tumor, can safely wait through manufacturing, and are being treated at a center experienced in complex cellular therapy.
Who may not be a candidate?
Rapidly progressive disease
Some patients may not remain clinically stable long enough to complete tumor harvest and manufacturing.
No accessible tumor
Current therapy requires a resectable lesion that can provide adequate viable tissue for manufacturing.
Major comorbidity or frailty
Lymphodepletion, interleukin-2, and hospitalization may be unsafe for patients with limited cardiopulmonary, renal, or functional reserve.
Low-burden or indolent disease
For some patients, the toxicity and resource burden may outweigh the immediate need for an intensive cellular approach.
What comes next
- Confirmation of clinical benefit in the phase III IOV-MEL-301 trial.
- Earlier-line testing of lifileucel in combination with pembrolizumab.
- Lower-intensity lymphodepletion and interleukin-2 strategies.
- Peripheral-blood approaches that may reduce dependence on surgical tumor harvest.
- Genetic and manufacturing innovations that enrich for neoantigen-reactive lymphocytes.
- Expansion of TIL therapy into other solid tumors.
Lifileucel demonstrates that individualized cellular therapy can be manufactured, regulated, and delivered at commercial scale for a solid tumor. Its approval may become a template for future cellular therapies across oncology.
Authors
Jennifer Strong, David M. Miller, and Isaac Brownell.