In this study, multiple myeloma participants with secondary immunodeficiency (SID) will be treated with HyQvia according to their clinic's standard practice. The study's main aim is to look into infusion parameters of HyQvia administration.

This is a prospective, observational study of adults having multiple myeloma (MM) with SID treated with HyQvia as part of routine clinical care. This study will characterize the real-world infusion parameters of HyQvia administration.

The study will enroll approximately 100 participants.

Study data will be requested through participants' routine clinic visits and patient-reported outcome (PRO)s are voluntary.

This multi-center trial will be conducted in selected European and South American countries. The overall time of this study is 38 months. Participants will make multiple visits to the clinic within 12 months after enrolment for follow-up assessments.

Inclusion Criteria:

Participants who meet all of the following criteria assessed at the time of enrollment are eligible for this study:

1. Ability and willingness to provide informed consent. For adult participants unable to provide informed consent, informed consent provided by the legally authorized representative (LAR).

2. Has a diagnosis of MM requiring systemic anti-myeloma therapy as per International Myeloma Working Group (IMWG) criteria.

3. Initiated HyQvia treatment as part of routine clinical care no more than 30 days before study enrollment or received no more than 2 doses of HyQvia treatment, whichever occurs first. Participants are also eligible if they newly start HyQvia within 30 days after the enrollment visit.

   Note: Participants who do not start HyQvia treatment within 30 days of enrollment will be considered as screen failures (and replaced).

4. Age >=18 years old at the time of MM diagnosis.

5. Available medical history records starting from the diagnosis of MM requiring systemic anti-myeloma therapy as IMWG criteria.

6. Life expectancy >6 months at the time of enrollment, per physician assessment.

7. Eastern Cooperative Oncology Group (ECOG) performance status score of <=2.

8. Participants/LAR willing and able to comply with the requirements of the protocol.

Exclusion Criteria:

Participants who meet any of the following criteria assessed at the time of enrollment are not eligible for this study:

1. Known hypersensitivity to any of the components of HyQvia.

2. Primary immunodeficiency (PID) or diagnosed with human immunodeficiency virus/acquired immunodeficiency syndrome (HIV/AIDS) and/or active hepatitis C and/or active hepatitis B infection.

3. Prior use of Ig treatment or prophylaxis within 3 months from the date of enrollment.

4. Serious infection(s) requiring intravenous (IV) treatment at the time of enrollment into the study; except for participants on short-term oral antibiotic therapy.

5. Has participated in an interventional clinical study involving a medicinal product or device within 30 days prior to enrollment or is scheduled to participate in an interventional clinical study involving a medical product or device during this study.

   Note: Participants on investigational chimeric antigen receptor-T (CAR-T) cell therapies and/or bispecific antibodies may participate.

6. Planned stem cell transplant during the treatment period or had a prior stem cell transplant: allogeneic transplant at any time, autologous transplant within 3 months of enrollment.

7. History of malignancy (other than MM) within 3 years before the date of enrollment (exceptions are squamous and basal cell carcinomas of the skin, carcinoma in situ of the cervix or breast, localized prostate cancer or other non-invasive lesion that in the opinion of the investigator, is considered cured with minimal risk of recurrence within 3 years).

8. Participant has had major surgery within 2 weeks before enrollment, or has not fully recovered from an earlier surgery, or has surgery planned during the time the participant is expected to participate in the study.

Note: Participants with planned surgical procedures to be conducted under local anesthesia may participate. Kyphoplasty or vertebroplasty are not considered major surgery.

The study population will include adult participants who suffer from MM, have a diagnosis of SID defined according to the European HyQvia label.

Takeda provides access to the de-identified individual participant data (IPD) for eligible studies to aid qualified researchers in addressing legitimate scientific objectives (Takeda's data sharing commitment is available on https://clinicaltrials.takeda.com/takedas-commitment?commitment=5). These IPDs will be provided in a secure research environment following approval of a data sharing request, and under the terms of a data sharing agreement.

IPD from eligible studies will be shared with qualified researchers according to the criteria and process described on https://vivli.org/ourmember/takeda/ For approved requests, the researchers will be provided access to anonymized data (to respect patient privacy in line with applicable laws and regulations) and with information necessary to address the research objectives under the terms of a data sharing agreement.