Made-to-Order TILs Effective Against Metastatic Melanoma

Neil Osterweil

April 15, 2021

In just over one third of patients with metastatic melanoma who had experienced disease progression while receiving multiple prior lines of therapy, including immunotherapy and targeted agents, objective clinical responses occurred with a customized cell therapy based on T cells extracted directly from tumor tissue.

The product, called lifileucel, is custom made for each patient and utilizes tumor-infiltrating lymphocytes (TILs) extracted from tumor lesions. This approach differs from other cell-based therapies, such as CAR T-cell therapy, which utilizes T cells collected from the patient's blood.

The new results come from a phase 2 trial conducted in 66 patients with previously treated unresectable or metastatic melanoma who received a single dose of the product. The objective response rate was 36.4%.

"Lifileucel has demonstrated efficacy and durability of response for patients with metastatic melanoma and represents a viable therapeutic option warranting further investigation," commented Jason Alan Chesney, MD, PhD, from the James Graham Brown Cancer Center, the University of Louisville, Louisville, Kentucky.

He presented the new data at the virtual American Association for Cancer Research (AACR) Annual Meeting 2021.

Customized cell therapy with TILs has been explored for the treatment of melanoma for more than a decade. Some researchers have reported durable response in 25% of patients.

However, "generalizing TIL therapy has been hampered by the complex and really not absolutely defined process for generating cells," commented Philip Greenberg, MD, professor and head of the program in immunology in the Clinical Research Division of the Fred Hutchinson Cancer Center, Seattle, Washington, who was the invited discussant.

The current study demonstrates that cell generation can be performed at a centralized facility that has the required technical expertise. The patient-specific products are then disseminated to multiple centers, he said. The study also demonstrates that TILs can be successfully generated from tumor sites other than skin or lymph nodes.

"Toxicity was, however, significant, although it was generally manageable, and it did occur early, generally within the first 2 weeks," he noted.

Patient-Derived Product

Lifileucel is a tailor-made immunotherapy product created from melanoma tumor tissues resected from lesions in skin, lymph nodes, liver, lung, peritoneum, musculoskeletal system, breast, or other visceral organs. The cells are shipped to a central manufacturing facility, whre the TILs are isolated, cultured, expanded, and reinvigorated. The cells are then harvested and cryopreserved. The process takes about 22 days. The cryopreserved product is then shipped back to the treating facility.

Prior to receiving the expanded and rejuvenated TILs, patients undergo myeloablative conditioning with cyclophosphamide followed by fludarabine. The TILs are then delivered in a single infusion, followed by administration of up to six doses of interleukin-2 (IL-2).

Details From Clinical Trial

At the meeting, Chesney reported details on the 66 patients in the trial. They had metastatic melanoma that was progressing on treatment. The mean number of prior lines of therapy was 3.3. All of the patients had received prior anti–programmed cell death protein–1 (PD-1) or programmed cell death–ligand-1 (PD-L1) agents; 53 had received a cytotoxic T lymphocyte protein 4 (CTLA-4) inhibitor; and 15 had received a BRAF/MEK inhibitor.

These patients had a mean of six baseline target and nontarget lesions, and 28 patients had liver and/or brain metastases.

Just over a third of patients (24 of 66, 36.4%) had an objective response; three patients had a complete response; and 21 had a partial response. In addition, 29 patients had stable disease, and nine experienced disease progression. Four patients had not undergone the first assessment at the time of data cutoff.

After a median follow-up of 28.1 months, the median duration of response was not reached. It ranged from 2.2 to >35.2 months.

Since the data cutoff in April 2020, reduction of tumor burden has occurred in 50 of 62 evaluable patients. Reductions in the target lesion sum of diameters has occurred in 11 patients. In one patient, a partial response converted to a complete response 24 months after infusion, Chesney noted.

The mean number of TILs infused was 27.3 billion (27.3 x 109). Appropriate amounts of TILs were manufactured from tumor samples acquired across all sites, and reductions in target lesion sum of diameter were seen across the range of TIL total cell doses.

All patients experienced at least one adverse event of any grade; all but two experienced grade 3 or 4 adverse events. Two patients died, one as a result of intraabdominal hemorrhage considered possibly related to TIL therapy, and one from acute respiratory failure deemed not related to TILs.

The most common grade 3 or 4 adverse events were thrombocytopenia, anemia, febrile neutropenia, neutropenia, hypophosphatemia, and lymphopenia.

"The adverse event profile was manageable and was consistent with the underlying and the known profiles of the nonmyeloblative depletion regimen and IL-2," Chesney said.

The decreasing frequency of adverse events over time reflects the potential benefit of the one-time infusion, and no new safety risks have been identified during more than 2 years of follow-up, he added.

Remaining Questions, Next Steps

Greenberg commented that the one of the limitations of the study is that the investigators did not characterize the TIL product.

"Studies have predicted that there's a particular type of cell, a stemlike T cell, that's responsible for mediating the efficacy," he commented. He referred to research from Steven Rosenberg, MD, PhD, and colleagues at the National Cancer Institute, where TILs were first used in 2002.

Greenberg also raised the question of whether high-dose IL-2 was required post infusion, given that the patients were lymphodepleted before receiving lifileucel.

Future steps for TIL therapy, he said, should include identification of biomarkers for success or failure; strategies to enhance generation and expansion of tumor-reactive T cells; postinfusion strategies, such as using vaccines and/or checkpoint inhibitors to increase therapeutic activity; genetic modifications to enhance the function of TILs in the tumor microenvironment; and research into other tumor types that may be effectively treated with TILs.

The study was supported by Iovance Biotherapeutics. Chesney has received research funding from Iovance and other companies and has consulted for Amgen and Replimune. Greenberg has served on scientific advisory boards, has received grant/research support, and owns stock in several companies that do not include Iovance.

American Association for Cancer Research (AACR) Annual Meeting 2021: Abstract CT 008. Presented April 10, 2021.

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