Off-the-Shelf NK Cell Products FT596 and FT516 Show Early Promise in B-cell Lymphoma

Regimens that included the off-the-shelf, induced pluripotent stem cell (iPSC)–derived natural killer (NK) cell products FT596 and FT516 were found to elicit encouraging responses with favorable tolerability when used in patients with B-cell lymphoma.¹

FT516 was engineered with a novel high-affinity, noncleavable CD16 Fc receptor, which is designed to maximize antibody-dependent cellular cytotoxicity by which NK cells recognize, bind, and eliminate antibody-coated cancer cells. FT596 comprises the hnCD16 Fc receptor and a CAR that targets CD19, which was designed to allow for the multiantigen targeting of cancer cells, and an interleukin (IL)-15 receptor fusion that strengthens the activity and survival of NK cells.

“We are pleased with the interim safety, response rates, and durability of responses observed in our ongoing clinical studies of FT516 and FT596 for the treatment of patients with relapsed/refractory B-cell lymphomas,” Scott Wolchko, president and chief executive officer of Fate Therapeutics, stated in a press release. “These data continue to demonstrate that our off-the-shelf, iPSC-derived NK cell product candidates can uniquely deliver substantial therapeutic benefit and expand patient access to cell-based cancer immunotherapies.”

Key Updates With FT596

In an ongoing phase 1 study (NCT04245722), FT596 is under investigation as a single-dose monotherapy and in combination with a single 375-mg/m² dose of rituximab (Rituxan) in patients with relapsed/refractory B-cell lymphoma. Treatment was given 3 days following conditioning chemotherapy comprised of 500 mg/m² of cyclophosphamide and 30 mg/m² of fludarabine.

At a data cutoff of June 25, 2021, a total of 10 patients in the monotherapy arm and 10 patients in the combination arm were determined to be evaluable for assessment of safety and efficacy in the first cohort of 30 million cells (n = 3 each), second cohort of 90 million cells (n = 4 each), and third cohort of 300 million cells (n = 3 each).

Participants previously received a median of 4 lines of therapy, with a median of 2.5 lines of therapy that comprised CD20-targeted therapy. Of the 20 evaluable patients, 60% had aggressive B-cell lymphoma, half (50%) were refractory to the most recent therapy they received, and 35% of patients had prior autologous CD19-targeted CAR T-cell therapy.

In the second and third cohorts of patients who received FT596 as a single agent (n = 14), 71% achieved an objective response with the agent; this included a 50% complete response (CR) rate per PET-CT scan and Lugano 2014 criteria on day 29. Notably, 80% of patients who had not received prior CD19-targeted CAR T-cell therapy (n = 10) responded to FT596; the CR rate in these patients was 50%.

Additionally, half of 4 patients who had prior CD19-targeted CAR T-cell therapy achieved a CR, and both patients had received treatment on the combination arm.

In the first cohorts of both the monotherapy and combination arms (n = 6), only 1 patient experienced an objective response with FT596, which was indicative of dose-response treatment effects for the product.

The FT596-containing regimens were found to be well tolerated with no dose-limiting toxicities (DLTs) experienced, and no reported any-grade treatment-emergent immune effector cell–associated neurotoxicity syndrome (ICANS) or graft-versus-host disease. However, 2 cases of cytokine release syndrome (CRS) were observed; 1 of the cases was grade 1 and the other was grade 2. Both cases occurred concurrently with other cofounding clinical events and resolved on the same day of onset.

The dose-escalation study of the product is ongoing, and patients are currently being enrolled to the fourth single-dose cohort of 900 million cells in each arm.

Perusing Progress Made With FT516

The phase 1 FT516-101 trial (NCT04023071) enrolled patients with histologically documented B-cell lymphoma that was expected to have CD20 expression.² Patients had to have relapsed/refractory disease following at least 1 previous systemic chemoimmunotherapy for which no available therapy was expected to produce a survival benefit. Moreover, patients needed to have measurable disease per Lugano classification and have previously undergone hematopoietic stem cell transplantation. Previous treatment with CAR T-cell therapies was allowed.

Participants received a regimen of 3 days of conditioning chemotherapy comprised of 500 mg/m² of cyclophosphamide and 30 mg/m² of fludarabine, a single dose of rituximab at 375 mg/m², and 3 weekly doses of FT516, which were each given with IL-2 cytokine support; this was given for 2 cycles. The investigative regimen was designed to be given in the outpatient setting.

The primary objective of the research was to identify DLTs and to determine the maximum-tolerated dose and maximum-assessed dose of FT516. Other areas of interest included evaluating the safety, tolerability, preliminary activity, pharmacokinetics, and immunogenicity of the FT516-containing regimens.

A total of 13 patients had been included on the trial and received FT516 and rituximab. The median age of these patients was 65 years (range, 28-75), with 46.2% of patients under 65 years and 53.8% of patients 65 years of age or older. Moreover, 61.5% of patients were female, 46.2% had a diffuse large B-cell lymphoma histology, 76.9% had stage IV disease at the time of study entry, and 69.2% had bulky disease. Additionally, the median number of prior regimens received was 3 (range, 1-7), with a median of 2 (range, 1-6) prior anti-CD20 regimens received. Just under half, or 46.2%, of patients were refractory, 7.7% had previously undergone transplant, and 38.5% had previously received CD19-targeted CAR T-cell therapy.

A total of 11 patients received the regimen in the second and third multi-dose cohorts of 90 million cells per dose (n = 4) and 300 million cells per dose (n = 7).

Results presented during the 2021 ASCO Annual Meeting showed that 8 of these 11 patients who received the regimen at a dose of 90 million cells or higher achieved an objective response rate (ORR) of 73% with the treatment; this included 4 of 5 patients who were refractory to their last regimen received. Moreover, 6 patients (55%) achieved a CR to treatment on day 29 following the second FT516 treatment cycle; notably, this included 2 patients (50%) who had experienced disease progression after previous autologous CAR T-cell therapy.

Notably, at 3 months after the first infusion of the regimen, all 8 responders maintained their response without requiring further therapeutic intervention.

As of a data cutoff date of July 7, 2021, 45% maintained their response without the need for additional therapeutic intervention; 4 of these patients continued to experience a CR, ranging from 4.6 months to 9.5 months, and 1 patient remained in partial response, at 6.1 months. Two patients who had experienced a CR went on to experience disease progression, and 1 patient who had achieve a PR with the regimen required additional anticancer treatment.

Notably, no DLTs were observed with the regimen and no serious or grade 3 or higher adverse effects associated with FT516 were reported. As such, the FT516 was well tolerated. No treatment-emergent CRS, ICANS, or GVHD was observed.

Dose escalation is currently ongoing in the fourth multi-dose cohort of 900 million cells per dose.

“At this time, we are initiating multiple indication-specific, dose-expansion cohorts to broadly assess FT516 in combination with CD20-targeted monoclonal antibody regimens, including in patients who have experienced disease progression following autologous CD19-targeted CAR T-cell therapy,” Wolchko added in the release.

References

1. Fate Therapeutics announces positive interim clinical data from its FT596 and FT516 off-the-shelf, iPSC-derived NK cell programs for B-cell lymphoma. News release. August 19, 2021. Accessed August 23, 2021. https://bit.ly/3kjOkXX
2. Strati P, Bachanova V, Goodman, A, et al. Preliminary results of a phase I trial of FT516, an off-the-shelf natural killer (NK) cell therapy derived from a clonal master induced pluripotent stem cell (iPSC) line expressing high-affinity, non-cleavable CD16 (hnCD16), in patients (pts) with relapsed/refractory (R/R) B-cell lymphoma (BCL). J Clin Oncol. 2021;39(suppl 15):7541. doi:10.1200/JCO.2021.39.15_suppl.7541