Study to Assess Safety of HDP-101 in Patients With Relapsed Refractory Multiple Myeloma

Inclusion Criteria:

• Male or female aged ≥18 years.

• Life expectancy >12 weeks.

• Eastern Cooperative Oncology Group Performance Status (PS) of 0 to 2.

• A confirmed diagnosis of active MM according to the diagnostic criteria establishedby the International Myeloma Working Group (IMWG).

• Must have undergone SCT or is considered transplant ineligible.

• Must have undergone prior treatments with antimyeloma therapy which must haveincluded an immunomodulatory drug, proteasome inhibitor, and anti-CD38 treatment,alone or in combination. In addition, the patient should either refractory orintolerant to any established standard of care therapy providing a meaningfulclinical benefit for the patient assessed by the Investigator.

• Measurable disease as per IMWG criteria.

• Adequate organ system function as defined in protocol.

Exclusion Criteria:

• For patient entering the Phase 2a part only: Prior treatment with any approved orexperimental BCMA-targeting modalities are not allowed.

• Known central nervous system involvement.

• Plasma cell leukemia.

• History of congestive heart failure.

• Autologous or allogenic SCT within 12 weeks before the first infusion or is planningfor autologous SCT.

• Symptomatic graft versus host disease post allogenic hemopoietic cell transplantwithin 12 months prior to the first study treatment infusion.

• Radiotherapy within 21 days prior to the first study treatment infusion.

• History of any other malignancy known to be active.

• Known human immunodeficiency virus infection.

• Patients with active infection requiring systemic anti-infective.

• Patients with positive test results for hepatitis B surface antigen or Hepatitis Bcore antigen.

• Patients with positive test results for hepatitis C virus (HCV) infection.

• Current active liver or biliary disease.