Study of ACTR087 in Combination With SEA-BCMA in Subjects With Relapsed or Refractory Multiple Myeloma

Inclusion Criteria:

- Signed written informed consent obtained prior to study procedures

- Histologically- or cytologically-confirmed relapsed or refractory multiple myeloma
(MM) with measurable disease

- Must have received at least 3 prior lines of therapy to include treatment with a
proteasome inhibitor (eg, bortezomib, carfilzomib, or ixazomib) and an
immunomodulatory agent (eg, lenalidomide, pomalidomide) unless double-refractory to
both; and a hematopoietic stem cell transplant (HSCT), for those subjects considered
HSCT-eligible.

- Quantitative serum IgG levels for subjects with IgG MM must not exceed the
institutional upper limit of normal (ULN)

- ECOG 0 or 1

- Life expectancy of at least 6 months

- Absolute neutrophil (ANC) count greater than 1000/ µL

- Platelet count greater than 50,000/µL

- Estimated GFR >30mL/min/1.73m2

Exclusion Criteria:

- Known active central nervous system (CNS) involvement by MM

- Systemic rheumatic or autoimmune diseases or acute or chronic infections

- Uncontrolled thromboembolic events or recent severe hemorrhage

- Subjects who are currently using more than 5mg/day of prednisone (or an equivalent
glucocorticoid exceeding physiologic replacement levels)

- Prior treatment as follows:

- T cell-directed antibody therapy (eg. Alemtuzumab, anti-thymocyte globulin)
within 6 months of enrollment

- Any prior myeloma-directed therapy including cytotoxic chemotherapy, biologic
therapy, or radiotherapy within 2 weeks of enrollment

- Any mAb or other protein therapeutic containing Fc-domains within 4 weeks of
enrollment

- Experimental agents within 3 half-lives prior to enrollment, unless progression
is documented on therapy

- Prior BCMA-directed investigational agents at any time

- Prior cell or gene therapy, excluding transfers of genetically unmodified
autologous cells (eg. Hematopoietic stem cell transplantation), at any time; or
prior allogeneic HSCT at any time

- Pregnant or breastfeeding