This is a Phase 2, randomized, open-label study evaluating the safety and efficacy of nogapendekin alfa inbakicept (NAI, ANKTIVA®) in combination with standard of care versus standard of care alone in critically ill adults with sepsis and persistent lymphopenia. The study aims to determine whether NAI can improve 28-day mortality by addressing the immunosuppressive phase of sepsis characterized by persistent lymphopenia (absolute lymphocyte count \<1,000 cells/µL). Participants will be randomized 1:1 to receive either NAI 1.2 mg subcutaneous injection on Days 3 (or earlier if ALC \<700 cells/µL), Day 14, and potentially Day 21 if ALC remains \<1,000 cells/µL, plus standard of care, or standard of care alone. The study will enroll approximately 50 participants (25 per arm) with persistent lymphopenia.