Inclusion Criteria:  Must be ≥18 years on the day of signing informed consent. Be willing and able to provide written informed consent/assent for the study. Eastern Cooperative Oncology Group (ECOG) performance status (PS) 0-1 Have received at least 2 prior lines of therapy and must be eligible for Kymriah therapy as SOC Subjects with relapsed or refractory LBCL after two or more lines of systemic therapy including diffuse large B-cell lymphoma (DLBCL), not otherwise specified (NOS), high grade B-cell lymphoma , and DLBCL arising from follicular lymphoma, must be eligible for Kymriah therapy as SOC. Subjects must have measurable disease by IWG response criteria for lymphoma [Lugano classification (1)] All subjects must consent to biopsies Subjects must have a life expectancy of greater than or equal to 12 weeks per assessment from the enrolling physician. Adequate organ and marrow function at the start of lymphodepleting chemotherapy as pre-conditioning for Kymriah infusion  Exclusion Criteria:  In Dose Escalation phase: Grade ≥2 CRS or ICANS post-Kymriah infusion. In Dose Expansion phase: Grade ≥3 CRS or ICANS post-Kymriah infusion. Pregnant, lactating or breastfeeding or expecting to conceive or father children within the study duration from screening through 120 days after the last dose of study treatment. Had previously received CD19-directed therapy Subjects with documented current central nervous system (CNS) involvement by lymphoma are to be excluded from study participation. Any concurrent chemotherapy or biologic or hormonal therapy for cancer treatment. Subjects who have autoimmune disease history for the past 2 years, including but not limited to systemic lupus erythematosus, rheumatoid arthritis, inflammatory bowel disease, vascular thrombosis associated with antiphospholipid syndrome, Wegener's granulomatosis, Sjögren's syndrome, Bell's palsy, Guillain-Barre syndrome, multiple sclerosis, vasculitis, or glomerulonephritis. Have active and clinically relevant bacterial, fungal, viral, or TB infection, including known Hepatitis A, B, or C or HIV (testing not required). Concurrent enrollment in another clinical study unless it is an observational (non interventional) clinical study. Receipt of any conventional or investigational anticancer therapy, not otherwise specified above, within 30 days prior to NT-I7 injection. Unresolved toxicities from prior anticancer therapy Receipt of live, attenuated vaccine within 30 days prior to NT-I7 injection. Has had an allogenic tissue/solid organ transplant or bone marrow transplant. Subjects for whom intramuscular therapy is contraindicated.