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Encouraging initial durability has been observed with afamitresgene autoleucel in patients with advanced synovial sarcoma or myxoid/round cell liposarcoma, according to data from the phase 2 SPEARHEAD-1 trial.
Encouraging initial durability has been observed with afamitresgene autoleucel (afami-cel) in patients with advanced synovial sarcoma or myxoid/round cell liposarcoma (MRCLS), according to data from the phase 2 SPEARHEAD-1 trial (NCT04044768) presented at 2021 ASCO Annual Meeting.1
As of the March 29, 2021, the evaluable population included 33 patients with synovial sarcoma and 4 with MRCLS. The overall response rate (ORR) for the intention-to-treat population was 39.4% with a disease control rate of 84.8%. Broken down by histology the ORR for patients with synovial sarcoma was 41.4% (n = 12) and 25.0% (n = 1) for patients with MRCLS. Of note, 2 complete responses were observed in patients with synovial sarcoma. Additionally, 1 partial response and stable disease in 2 other patients were reported for patients with MRCLS.
The median duration of response has not yet been reached (range, 4.3+–38.0+).
“The responses [with afami-cel] appear to be protracted, deep, and durable,” Sandra P. D’Angelo, MD, explained in a presentation of the data adding that the data is “encouraging.” D’Angelo is a medical oncologist at Memorial Sloan Kettering Cancer Center in New York, New York.
Afami-cel is a specific peptide enhanced affinity receptor (SPEAR) T-cell therapy that is engineered to target MAGE-A4 peptide expressed on tumor cells. In the context of HLA-A*02, MAGE-A4 is highly expressed in synovial sarcoma and MRCLS.2 The T-cell therapy previously demonstrated clinical activity in in various tumors in a phase 1 study (NCT03132922). At the time of data cutoff all partial responses reported for the trial were in patients with synovial carcinoma.3
SPEARHEAD-1 is designed to further evaluate the safety and efficacy of afami-cel in HLA-A*02 eligible and MAGE-A4-positive patients with metastatic or advanced synovial sarcoma or MRCLS. Patients must have previously received either an anthracycline- or ifosfamide-containing regimen. The primary end point is ORR. Disease is assessed using CT/MRI every 4 weeks for 6 months and then every 2 months after that via independent review per RECIST v1.1.2 Secondary outcomes include duration of response, time to response, progression-free and overall survival.
Prior to afami-cel infusion, patients received lymphodepleting chemotherapy consisting of fludarabine (30 mg/m2 daily for 4 days) and cyclophosphamide (600 mg/m2 daily for 3 days). Patients then received a single infusion of autologous genetically modified afami-cel at a dose of 1 to 10 × 109 transduced T cells.2
At the time of presentation, 330 patients were screened for HLA-A*02 and of those 176 were determined to have positive disease.1 From these patients, 106 were determined to have MAGE-A4 expression in at least 30% of tumor cells that were at least 2+ as determined by immunohistochemistry.4 In total, 59 patients were enrolled and underwent leukapheresis across the 2 cohorts of the study and 37 were treated with afami-cel. Sixteen patients are awaiting treatment and 5 discontinued prior to T-cell therapy.1
At the time of data cutoff, 4 patients who received afami-cel were still awaiting their first efficacy assessment and were not included in the initial analysis.
Of the 37 evaluable patients, the median age was 42 years (range, 24-73) and has a median of 3 prior lines of systemic therapy (range, 1-12). The median cell dose was 8.8 × 109 (range, 2.7-9.9).
In terms of safety, treatment-emergent adverse effects (TEAEs) were consistent with those observed for patients who undergo cytotoxic chemotherapy, D’Angelo noted. “The most common TEAEs were likely related to the lymphodepleting regimens [with the] incidence of cytopenia in a majority of patients, with a majority being grade 3 or greater in severity,” she said.
Specifically, the most common TEAEs of any grade were lymphopenia (84%), neutropenia (73%), nausea (65%), and pyrexia (51%). Two AEs were of special interest: cytokine release syndrome and grade 3 or higher prolonged cytopenia at 4 weeks post infusion.
Cytokine release syndrome of any grade was observed in 22 patients (59%) and was grade 3 or higher in 1 patient (3%). The median time to onset was 3 days (range, 1-9) and the median time to resolution was 3 days (range, 1-34). D’Angelo highlighted that more than half (55%) of patients with cytokine release syndrome required treatment with tocilizumab (Actemra).
“Patients often experience cytopenia on these clinical trial for several weeks following lymphodepletion and T-cell infusion. We have seen neutropenia, thrombocytopenia, and anemia of grade 3 or greater in less than 10% of patients,” D’Angelo said. Of the 37 patients treated, 2 experienced grade 3 or higher neutropenia, 1 had thrombocytopenia, and 3 had anemia at the 4-week post infusion analysis.
Additionally, D’Angelo highlighted early analysis of responses that demonstrated clinical activity across a wide range of MAGE-A4 H-scores and cell doses. “Translational data from this trial are continuing to be evaluated and early results from 13 patients with clinical responses [are available] to date,” D’Angelo said.
The median H-score via immunohistochemistry was 225 (range, 134-300) and the median cell dose in the responders was 6.45 × 109 (range, 2.7-9.9).
Primary efficacy analysis will be for cohort 1 of the trial and enrollment is complete, according to the agent’s developer Adaptimmune Therapeutics.4
“SPEARHEAD-1 is ongoing and data from this trial will be used to support Adaptimmune’s BLA [biologic license application] submission next year ,” D’Angelo said.