A Phase 1, First-in-Human, Dose Escalation Study of MGD024, a CD123 x CD3 Bispecific DART Molecule, in Patients with Select Relapsed or Refractory Hematologic Malignancies

CP-MGD024-01 is a Phase 1, open-label, multi-center study of MGD024 as a single agent in
participants with select blood cancers that have not responded to treatment with standard
therapies or who have relapsed after treatment. The study is designed to determine the
safety, tolerability, pharmacokinetics (affect of the body on the drug), pharmacodynamic
(affect of the drug on the body), immunogenicity (development of antibodies against the
drug), and preliminary anti-cancer effect of MGD024.

Participants will receive treatment with MGD024 in consecutive 28-day cycles for a study
treatment period of up to 12 cycles (approximately 1 year) or until treatment or study
discontinuation criteria are met. Response assessments will be performed after Cycle 1
and then after every even numbered cycle starting with Cycle 2 until progression or study
treatment discontinuation. Participants will be checked for side effects throughout the
study.

Inclusion Criteria:

- Adult patients at least 18 years of age, able to provide informed consent and
willing to comply with all study procedures.

- Participants with

- primary or secondary acute myeloid leukemia (AML) except acute promyelocytic
leukemia,

- primary or secondary myelodysplastic syndrome (MDS) with prognostic score of >3
and <20% bone marrow blasts,

- classical Hodgkin lymphoma (cHL),

- chronic myelogenous leukemia (CML),

- b-cell acute lymphocytic leukemia (B-ALL),

- hariy cell leukemia (HCL),

- advanced systemic mastocytosis (ASM), or

- blastic plasmacytoid dendritic cell neoplasm (BPDCM)

- Relapsed after or refractory to at least one prior line of therapy and with no
available potentially curative treatment option.

- Evidence of at least 20% of malignant cells with CD123 expression.

- Eastern Cooperative Oncology Group (ECOG) performance status of ≤ 2.

- Life expectancy of at least 12 weeks.

- Acceptable laboratory values, and heart function.

- Continuing side effects of prior treatment are mild

- Women and men of childbearing potential must agree to use highly effective forms of
contraception throughout the study through 4 months after the last dose of MGD024.

Exclusion Criteria:

- Prior treatment with an anti-CD123-directed agent (except patients with BPDCN, who
are allowed to have received prior tagraxofusp).

- Known involvement of central nervous system (CNS) by the disease under
investigation.

- History or current evidence of any condition, therapy, or laboratory abnormality
that might confound the results of the trial, interfere with the patient's
participation for the full duration of the trial, or is not in the best interest of
the patient.

- Systemic anti-cancer therapy, investigational therapy, corticosteroids or other
immune suppressive drugs within 14 days of first dose

- Vaccination with any live virus vaccine within 4 weeks prior to first dose.
Inactivated annual influenza and SARS-CoV-2 vaccination are allowed.