Background: CD47 is an innate immune checkpoint that binds signal regulatory protein alpha (SIRPα) and delivers a "don’t eat me" signal to suppress macrophage phagocytosis. TTI-622 is a fusion protein consisting of the CD47-binding domain of human SIRPα linked to the Fc region of human IgG4. It is designed to enhance phagocytosis and antitumor activity by preventing CD47 from delivering its inhibitory signal as well as generating a moderate pro-phagocytic signal via IgG4 Fc. CD47 is significantly increased in multiple myeloma (MM) bone marrow mononuclear cells and expression inversely correlates with survival in patients. Relapsed/Refractory (R/R) MM shows particularly high expression of CD47. Preclinical studies demonstrate that the addition of proteasome inhibitors to CD47 blockade significantly increases phagocytosis of MM cells in vitro and anti-myeloma activity in vivo. The ongoing phase 1a part of this study has been previously described. The phase 1b part of the study will determine the safety and efficacy of TTI-622 when given as monotherapy or in combination with selected approved anticancer treatments in patients with hematological malignancies where new treatments with novel mechanism of action are needed. Here we describe 5 RRMM cohorts within phase 1b of the study. Methods: TTI-622-01 is a multi-center Phase 1a/1b study. Phase 1a was designed to determine the MTD, pharmacokinetics (PK), pharmacodynamics, and preliminary antitumor activity of QW, Q2W, and Q3W single-agent TTI-622 in R/R lymphoma using a 3+3 dose escalation schema. Phase 1b, ongoing, will determine the safety and recommended dose of TTI-622 to be given as single agent and in combination with carfilzomib + dexamethasone (Kd) in RRMM and will evaluate the preliminary efficacy. Secondary objectives are to further characterize the safety, PK and immunogenicity of TTI-622 when combined with Kd. Patients will be enrolled in 5 separate cohorts: 3 cohorts will explore different doses and administration schedules of TTI-622 combined with the approved dose of Kd; 2 cohorts will explore different doses of TTI-622 monotherapy. Cohorts will be opened in a staggered manner. In each cohort 3 patients will be dosed and followed for 28 days (21 days in the monotherapy) before expanding enrolment to approximately an additional 27 patients. Key eligibility criteria include: relapse or progression following ≥3 prior lines of therapy (including a proteasome inhibitor, an immunomodulatory drug, and an anti-CD38 antibody), carfilzomib-refractory progressive and measurable disease per IMWG at study entry; age ≥18 years; ECOG performance status ≤2; adequate organ functions; no known CNS involvement; no prior anti-CD47 or anti-SIRPα therapy. Patient recruitment is planned or ongoing at 40 sites worldwide. Clinical trial information: NCT03530683.