MBL deficient patients enrolled in this protocol are scheduled to be treated with melphalan-based high-dose chemotherapy followed by autologous hematopoietic stem cell transplant (HSCT) for their multiple myeloma. Patients are randomized to 0.5 mg/kg, 1.0 mg/kg, or no rhMBL.

MBL deficient patients will be randomized in a ratio of 2:2:1 to receive up to 4 weekly i.v. infusions of rhMBL at a dose of 0.5 mg/kg or 1.0 mg/kg, or standard anti-infectious prophylactic therapy alone. A total of 20 patients will be treated in each of the rhMBL arms, and 10 patients will receive best standard supportive prophylactic therapy but not rhMBL. All patients are to receive anti-infectious prophylactic supportive therapy as per institutional standards.

Major Inclusion Criteria: Patients must meet all of the following criteria to be eligible for enrollment into the study:

• Capable of understanding the protocol requirements and risks and providing written informed consent.
• Histologically or cytologically confirmed diagnosis of multiple myeloma.
• Mannose-binding lectin level <300 ng/mL.
• Age ≥18 years old.
• Score of 0 to 2 on the Zubrod performance status scale.
• Patient is scheduled to receive melphalan-based high-dose chemotherapy and autologous HSCT for the treatment of multiple myeloma.

Exclusion Criteria:

• Concurrent serious medical illness that could potentially interfere with protocol compliance.
• Concurrent or previous malignancy associated with a poor prognosis.
• Known chronic infectious disease, such as acquired immunodeficiency syndrome (AIDS) or hepatitis (for hepatitis and human immunodeficiency virus [HIV] will not be performed).
• Positive screening pregnancy test or is breast-feeding.
• Female or male patient of reproductive capacity unwilling to use methods appropriate to prevent pregnancy during the course of this protocol.
• Known or clinically suspected active brain metastases.
• Current participation in another clinical study with an investigational agent and/or use of an investigational drug.