Study of STRO-001, an Anti-CD74 Antibody Drug Conjugate, in Patients With Advanced B-Cell Malignancies

This study is a first-in-human Phase 1, open-label, multicenter, dose escalation study with
dose expansion to identify the maximum tolerated dose (MTD), the recommended phase 2 doses
(RP2D) and to evaluate the safety, tolerability, and preliminary anti-tumor activity of
STRO-001 in adult subjects with B-cell malignancies (MM and NHL) who are refractory to, or
intolerant of, all established therapy known to provide clinical benefit for their condition
(i.e., trial subjects must not be candidates for any regimens known to provide clinical
benefit). The study will consist of two parts: Part 1, dose escalation, and Part 2, dose
expansion.

During Part 1 (dose escalation), an accelerated dose titration design will be applied to
cohorts A (MM) and B (NHL). Doses will be escalated using an N-of-1 until the first instance
of a treatment-related, clinically relevant Grade 2 non-hematologic toxicity or a Grade 3
hematologic toxicity of any type is observed during Cycle 1 (first 28 days). Any event
meeting these criteria will be reviewed and confirmed by the Safety Evaluation Team (SET).
Each dose escalation cohort will be assessed independently. When these criteria are met then
the dose is expanded with 2 additional subjects and the standard 3+3 trial design is used for
all further dosing cohorts. The dose escalation (Part 1) phase of the study will be complete
when the MTD is determined and the recommended dose for Part 2 (dose expansion) is
identified. The RP2D will be selected based on the safety, tolerability and exposure of
STRO-001, and will be the end of Part 1 of the study. After determination of the RP2D,
subjects with MM or NHL will be enrolled into indication specific dose expansion cohorts
(Part 2). The accelerated dose titration (N-of-1) design with seamless transformation into a
traditional 3+3 design allows for very low starting doses to be evaluated in fewer patients.

In both Part 1 and Part 2 of the study, STRO-001 will be dosed as an intravenous (IV)
infusion on Day 1 and Day 15 in 28-day cycles, until disease progression. Labs will be drawn
on a weekly basis for Cycles 1-3, and every two weeks starting with Cycle 4. Weekly clinical
evaluations will be conducted during Cycle 1; thereafter, clinical evaluations will be
conducted on infusion days (Day 1 and Day 15 of each cycle). Samples for pharmacokinetics
(PK) analysis will occur at specific times on Days 1, 2, 3, 8, 15, 16, 22, and 29 of
treatment and at end of treatment visit. Additional clinical evaluations and labs may occur
at the discretion of the investigator.

Subjects who receive any dose of STRO-001 will be included in safety analyses. Disease
evaluations will include peripheral blood analysis, bone marrow assessments and scans as
appropriate. Disease status will be evaluated per MM-specific or NHL-specific criteria.
Samples will be collected to assess the PK and immunogenicity of STRO-001. Biomarkers may be
assessed from bone marrow, peripheral blood and/or tissue samples. Subjects will continue to
receive study drug until disease progression, unacceptable toxicity, withdrawal of consent,
or end of study (study completion).

Key Inclusion Criteria:

1. Confirmation of diagnosis

2. Relapsed or relapsed/refractory disease

3. Age ≥ 18 years

4. ECOG performance status (0-2)

5. Life expectancy > 3 months

6. Adequate bone marrow and renal functions

7. QTcF <500 msec

8. Ability to comply with treatment, PK and test schedules

9. NHL only- at least one measurable lesion

Key Exclusion Criteria:

1. Active plasma cell leukemia and/or leukemic manifestations of lymphoma

2. Known amyloidosis (MM patients)

3. Chronic lymphocytic leukemia and Richter's transformation, and prolymphocytic leukemia
(NHL subjects)

4. T-cell malignancy

5. Sensory or motor neuropathy ≥ grade 2

6. Chronic or ongoing active infectious disease requiring systemic treatment such as, but
not limited to, chronic renal infection, chronic chest infection with bronchiectasis,
tuberculosis and active hepatitis C

7. Ongoing immunosuppressive therapy, including systemic corticosteroids. Note: Subjects
may be using topical or inhaled corticosteroids.

8. Clinically significant cardiac disease

9. Significant concurrent, uncontrolled medical condition

10. History or clinical signs of meningeal or active CNS involvement

11. Known severe chronic obstructive pulmonary disease or asthma

12. History of significant cerebrovascular disease

13. Known Human Immunodeficiency Virus seropositivity

14. Positive serology for hepatitis B defined by a positive test for HBsAg

15. Concurrent participation in another therapeutic treatment trial

16. High screening liver function tests

17. Prior treatment with CD74 targeting therapy

18. Patients requiring anti-coagulant therapy