Abstract CT522: Feasibility and safety of a novel CD19 CAR T cell therapy in adults with R/R B-NHL

Genetically engineered chimeric antigen receptor (CAR) T cells have exhibited distinct effectiveness against chemotherapy refractory CD19 expressing B cell malignancies in both adults and children. This phase I clinical trial tests a novel anti-CD19 CAR T cell product in adults with relapsed/refractory (R/R) B-cell Non-Hodgkin’s Lymphoma (B-NHL). The CAR construct is comprised of the short chain variable regions of the anti-CD19 monoclonal antibody FMC63, the TNFRSF19-derived transmembrane domain, the 4-1BB costimulatory domain, and the CD3-zeta signaling domain. CD19 CAR T cells were manufactured utilizing the CliniMACS Prodigy® T Cell Transduction Process (CD3/CD28 TransAct™ reagent) allowing for highly automated production, with IL-7 and IL-15 used for T cell expansion for 8-12 days. To date, 7 patients have been treated with an average dose of 1.2 ± 0.2 x 108 CAR T cells. The histology includes marginal zone lymphoma (n=1), follicular lymphoma Grade IIIA (n=1), transformed lymphoma (n=3), follicular lymphoma low grade (n=2), and diffuse large B-cell lymphoma (n=1). One patient required a second apheresis due to poor cell expansion. Despite heterogeneity in disease subtype and leukapheresis product quality, CAR T production and expansion have been consistent with final transduction efficiencies between 14-45%, cell viability between 88-91%, and an overall average yield of 3.2 ± 0.3 x 109 cells before harvest, allowing for product banking. No safety-related out of specifications (OOS) events have occurred, however, 2 patients had OOS product infused due to low transduction efficiency (both at 14% rather than the ≥ 20% release criteria). Two patients experienced Grade 2 CRS, 1 patient experienced Grade 2 neurotoxicity; otherwise, no new safety signals were detected. Disease response was assessed on Days 90, 180, 270, and 360 post-infusion. The assessments were based on 2014 Lugano criteria. Even with 2 OOS products, Day 90 scans showed a complete metabolic remission (CMR) in 6 evaluable patients to date. Of the 6 patients with CMR, 1 patient progressed at Day 180 and the others remain in remission (median f/u = 12 months). Flow cytometry was utilized to measure CAR T cell peak expansion and persistence in 5 patients. Peak CAR T cell expansion (2.9-44.4% of CD3 cells) ranged from Day 5 to 15. Cell persistence was detected for the 5 patients through at least Day 180. ddPCR is currently in development to perform persistence testing in parallel. Additionally, cytokine concentrations including INFγ, IL-10, IL-12p70, IL-13, IL1β, IL-2, IL-4, IL-6, IL-8, and TNFα were evaluated over the first 30 days. Overall, 7 patients diagnosed with 5 different B-NHL subtypes have been treated with the CD19 CAR T cell product. Manufacturing was successful for all patients with no safety related OOS, and no new post-infusion safety signals detected. To date, 6 out of 7 patients are alive, 5 with CMR and with CD19 CAR T cell persistence through at least 180 days.

Citation Format: Manali Kamdar, Cheri Adams, Steven Bair, Boro Dropulic, Jonathon Gutman, Bradley Haverkos, Kimberly Jordan, Rebecca Mallo, Russell Marians, Felicia Mast, Lindsey Murphy, Andrew Roth, Matthew Seefeldt, Andrew Worden, Mike Kadan, Ying Xiong, Dina Schneider, Rimas Orentas, Terry Fry, Michael Verneris. Feasibility and safety of a novel CD19 CAR T cell therapy in adults with R/R B-NHL [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr CT522.

Sterol regulatory element binding protein and dietary lipid regulation of fatty acid synthesis in the mammary epithelium

The lactating mammary gland synthesizes large amounts of triglyceride from fatty acids derived from the blood and from de novo lipogenesis. The latter is significantly increased at parturition and decreased when additional dietary fatty acids become available. To begin to understand the molecular regulation of de novo lipogenesis, we tested the hypothesis that the transcription factor sterol regulatory element binding factor (SREBF)-1c is a primary regulator of this system. Expression of Srebf1c mRNA and six of its known target genes increased ≥2.5-fold at parturition. However, Srebf1c-null mice showed only minor deficiencies in lipid synthesis during lactation, possibly due to compensation by Srebf1a expression. To abrogate the function of both isoforms of Srebf1, we bred mice to obtain a mammary epithelial cell-specific deletion of SREBF cleavage-activating protein (SCAP), the SREBF escort protein. These dams showed a significant lactation deficiency, and expression of mRNA for fatty acid synthase (Fasn), insulin-induced gene 1 (Insig1), mitochondrial citrate transporter (Slc25a1), and stearoyl-CoA desaturase 2 (Scd2) was reduced threefold or more; however, the mRNA levels of acetyl-CoA carboxylase-1α (Acaca) and ATP citrate lyase (Acly) were unchanged. Furthermore, a 46% fat diet significantly decreased de novo fatty acid synthesis and reduced the protein levels of ACACA, ACLY, and FASN significantly, with no change in their mRNA levels. These data lead us to conclude that two modes of regulation exist to control fatty acid synthesis in the mammary gland of the lactating mouse: the well-known SREBF1 system and a novel mechanism that acts at the posttranscriptional level in the presence of SCAP deletion and high-fat feeding to alter enzyme protein.

Alternative pathway of complement in children with diarrhea-associated hemolytic uremic syndrome

BACKGROUND AND OBJECTIVES

Diarrhea-associated hemolytic uremic syndrome (D+HUS) is a common cause of acute kidney injury in children. Mutations in alternative pathway (AP) complement regulatory proteins have been identified in severe cases of thrombotic microangiopathy, but the role of the AP in D+HUS has not been studied. Therefore, we determined whether plasma levels of markers of activation of the AP are increased in D+HUS and are biomarkers of the severity of renal injury that predict the need for dialysis.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

Patients were randomly selected from among participants in the HUS-SYNSORB Pk trial. Plasma samples were collected on days 1, 4, 7, and 10 after enrollment and day 28 after discharge from the hospital. Levels of two complement pathway products, Bb and SC5b-9, were determined by ELISA.

RESULTS

Seventeen children (6 boys and 11 girls; age, 5.4 +/- 3.5 yr) were studied. Eight (47%) required dialysis support, and two had serious extrarenal events. On the day of enrollment, plasma levels of Bb and SC5b-9 were significantly increased in all patients compared with healthy controls (P < 0.01). The elevated concentrations normalized by day 28 after discharge. Circulating levels of complement pathway fragments did not correlate with severity of renal injury or occurrence of complications.

CONCLUSIONS

Patients with acute-onset D+HUS manifest activation of the AP of complement that is temporally related to the onset of disease and that resolves within 1 mo. Therapies to inhibit the AP of complement may be useful in attenuating the severity of renal injury and extrarenal complications.

Alternative pathway of complement in children with diarrhea-associated hemolytic uremic syndrome

BACKGROUND AND OBJECTIVES

Diarrhea-associated hemolytic uremic syndrome (D+HUS) is a common cause of acute kidney injury in children. Mutations in alternative pathway (AP) complement regulatory proteins have been identified in severe cases of thrombotic microangiopathy, but the role of the AP in D+HUS has not been studied. Therefore, we determined whether plasma levels of markers of activation of the AP are increased in D+HUS and are biomarkers of the severity of renal injury that predict the need for dialysis.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

Patients were randomly selected from among participants in the HUS-SYNSORB Pk trial. Plasma samples were collected on days 1, 4, 7, and 10 after enrollment and day 28 after discharge from the hospital. Levels of two complement pathway products, Bb and SC5b-9, were determined by ELISA.

RESULTS

Seventeen children (6 boys and 11 girls; age, 5.4 +/- 3.5 yr) were studied. Eight (47%) required dialysis support, and two had serious extrarenal events. On the day of enrollment, plasma levels of Bb and SC5b-9 were significantly increased in all patients compared with healthy controls (P < 0.01). The elevated concentrations normalized by day 28 after discharge. Circulating levels of complement pathway fragments did not correlate with severity of renal injury or occurrence of complications.

CONCLUSIONS

Patients with acute-onset D+HUS manifest activation of the AP of complement that is temporally related to the onset of disease and that resolves within 1 mo. Therapies to inhibit the AP of complement may be useful in attenuating the severity of renal injury and extrarenal complications.