On June 4, 2021 Precision BioSciences Inc. (Nasdaq: DTIL), a clinical stage biotechnology company developing allogeneic CAR T and in vivo gene correction therapies with its ARCUS genome editing platform, reported encouraging progress on two strategies designed to optimize the durability of allogeneic CAR T therapy in patients with relapsed/refractory (R/R) non-Hodgkin lymphoma (NHL) (Press release, Precision Biosciences, JUN 4, 2021, View Source [SID1234583521]). The Company reported updated interim results from its Phase 1/2a study of PBCAR0191, the Company’s investigational, off-the-shelf, allogeneic CAR T cell therapy targeting CD19. As of May 21, 2021, 12 patients with R/R NHL were enrolled and evaluated for response to PBCAR0191 with enhanced lymphodepletion (eLD). The Company also reported preclinical data demonstrating the potential mechanism by which its investigational immune evading stealth cell, PBCAR19B, may avoid rejection by T cells and natural killer (NK) cells.

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"These interim results in heavily pretreated R/R NHL patients illustrate the potential for PBCAR0191 to recognize and target CD19 positive cancer cells and suggest that enhanced lymphodepletion may be a strategy to help suppress host immune rejection. We’re encouraged by the high initial response rates and look forward to monitoring the responses for evidence of long-term durability," said Alan List, MD, Chief Medical Officer of Precision BioSciences. "In addition, our PBCAR19B Phase 1 study is open for enrollment, and we believe this candidate has the potential to build on the encouraging clinical responses we’ve seen with PBCAR0191 to date and reduce the need for prolonged immunosuppression."

As of May 21, 2021, 18 subjects in the Phase 1/2a study of PBCAR0191 with R/R NHL completed Day 28 evaluation and received either eLD1 (n=12) or standard lymphodepletion2 (sLD; n=6) with Dose Level 33 of PBCAR0191.

Efficacy

Use of eLD mitigated PBCAR0191 rejection and markedly increased peak cell expansion (~72x) and area under the curve (AUC) (~59x), each as compared to sLD.
A single dose of PBCAR0191 cells following eLD yielded clinical responses in the majority of patients, with overall response rates (ORR) and complete response (CR) rates of 75% and 50%, respectively at Day ≥ 28.
Five of nine responding patients (56%) who received PBCAR0191 cells following eLD remained progression-free, including 4/9 evaluable subjects with responses lasting > 4 months. Assessment of duration of response is on-going.
Median interval from confirmation of eligibility to start of LD was 1 day, reinforcing the potential feasibility for rapid delivery of off-the-shelf, allogeneic, cellular therapy for high-risk patients.
Day ≥ 28 Evaluation

* Three of four responding patients had prior auto-SCT and auto CD19 CAR treatment.

Safety and Tolerability

As of May 21, 2021, PBCAR0191 with eLD continued to show acceptable tolerability without evidence of graft versus host disease (GvHD) and with a similar frequency of immune effector cell-associated neurotoxicity syndrome (ICANS) and cytokine release syndrome (CRS) compared to patients who received sLD. Infections occurred more frequently when PBCAR0191 was dosed following eLD.

Adverse Event Max Grade

(Graft versus host disease)

Three treatment emergent deaths without disease progression occurred, including two cases of infection and one case of cardiac arrest after a choking incident. Two of these patients were in ongoing complete responses at time of death. Only one death, as previously reported on December 4, 2020 was assessed by the investigator as possibly related to study treatment.

Demographics for Enrolled R/R NHL Patients (PBCAR0191 with eLD)

Over 80% of subjects had advanced and aggressive lymphomas.
75% had stage III/IV disease.
Subjects had received a median of seven lines of therapy prior to study enrollment.
33% of subjects had prior CD19-directed CAR therapy.
PBCAR19B Immune Evading Stealth Cell

PBCAR19B is designed to extend persistence of allogeneic CAR T cells by evading rejection by the immune system of the patient. In preclinical studies, the anti-CD19 PBCAR19B stealth cell exhibited substantial resistance to rejection mediated by both allo-reactive T cell and NK cells, suggesting the potential utility of this approach.

In January 2021, Precision announced that the U.S. Food and Drug Administration accepted its investigational new drug application to evaluate the safety and clinical activity of PBCAR19B in patients with R/R NHL. Initial clinical trial sites have been selected for the Phase 1 study that is now open for enrollment. PBCAR19B will be evaluated at increasing flat dose levels beginning at 2.7 x 108 cells using sLD with the ability to dose up to 8.1 x 108 cells. Of note, the first dose level is approximately equivalent to Dose Level 3 in the PBCAR0191 trial.

Company-Hosted Conference Call and Web Cast Information

Precision will host a conference call and webcast today, Friday, June 4, 2021 at 8:00 a.m. ET to discuss the most recent interim clinical data for PBCAR0191 and preclinical data for PBCAR19B. The dial-in conference call numbers for domestic and international callers are (866) 996-7202 and (270) 215-9609, respectively. The conference ID number for the call is 5647916. Participants may access the live webcast and the accompanying presentation materials on Precision’s website www.precisionbiosciences.com in the Investors and Media section under Events and Presentations. An archived replay of the webcast will be available on Precision’s website.

About PBCAR0191 and Study Design (Clinical Trials Study Identifier: NCT03666000)

PBCAR0191 is an investigational allogeneic chimeric antigen receptor T cell therapy (CAR T) in a Phase 1/2a trial for the treatment of patients with R/R NHL and R/R B-ALL. PBCAR0191 was designed using Precision BioSciences novel and proprietary ARCUS genome editing platform. It has been granted Fast Track Designation by the FDA for B-ALL. Precision also holds Orphan Drug Designation from the FDA for this program in mantle cell lymphoma, an aggressive subtype of NHL.

About PBCAR19B (Clinical Trials Study Identifier: NCT04649112)

PBCAR19B is a next-generation, stealth cell candidate for patients with CD19-positive malignancies such as R/R NHL. PBCAR19B is designed to improve the persistence of allogeneic CAR T cells following infusion by reducing rejection by T cells and NK cells. In addition to the CAR gene, the PBCAR19B stealth cell vector carries a short hairpin RNA that suppresses expression of beta-2 microglobulin, a component of Major Histocompatibility Complex (MHC) Class I molecules found on the cell surface. Reducing or knocking-down Class I MHC expression on allogeneic CAR T cells has been shown to reduce CAR T cell killing by cytotoxic allo-reactive T cells. Additionally, in an effort to attenuate NK cell-mediated elimination due to MHC class I knockdown, the PBCAR19B vector also carries an HLA-E gene designed to inactivate NK cells.