MCLA-117 in Acute Myelogenous Leukemia

Study Design :

This open label, single arm, multinational, first-in-human study consists of 2 parts. Part 1
consists of dose escalation cohorts and Part 2 is a dose expansion cohort.

The study population will include adult AML patients (and all subtypes of AML) with relapse
or refractory disease and newly diagnosed elderly untreated AML patients with high risk
cytogenetics.

In Part 1, dose escalations cohorts are followed until dose-limiting toxicity (DLT) or a
maximum tolerated dose (MTD) or RecommendedPart2Dose (RP2D) is defined. Dose escalation
decisions will be made by the Data Review Committee and will be primarily guided by safety
data observed through the end of Cycle 1, as well as on-going assessment of safety beyond
Cycle 1 in later cohorts.

Part 2 will begin once the MTD or RP2D is determined in Part 1. Part 2 will further
characterize the safety, tolerability, Pharmacokinetic (PK), Pharmacodynamic (PD),
immunogenicity and to assess preliminary efficacy of MCLA-117. This part will enroll at least
15 evaluable patients (defined as evaluable for first efficacy assessment).

For both parts, the study consists of 3 periods: a Screening period (up to 28 days prior to
the first dose of study drug); a Treatment period (first dose of study drug until the last
dose of study drug with treatment cycles of 28 days); and a Follow Up period (through 30 days
after the last dose and quarterly checks for survival data for up to 1 year). Participants'
safety will be monitored throughout the study. Patients will be permitted to receive MCLA-117
beyond Cycle 1 if conditions allow this.

Number of Sites:

Approximately 8 centers in five countries are estimated to be involved during Parts 1 and 2
of the study. Additional sites may be added to ensure there is an acceptable enrollment rate
or to replace non-enrolling/withdrawn sites.

Inclusion Criteria:

1. Male or female age ≥18 years old;

2. Signed informed consent form

3. AML either de novo or secondary [any subtype except acute promyelocytic leukemia
(APL)] who either:

1. are in relapse to standard therapy following an initial response

2. failed primary induction therapy with no CR (failed ≥2 induction attempts) and
for whom no other approved therapy is available

3. newly diagnosed untreated AML in patients ≥ 65 years of age with high risk
cytogenetics, if they are not candidates for standard available induction
chemotherapy

4. Must have baseline BM sample taken by BMA/BMB within 21 days prior to first dose of
MCLA-117 for CLEC12A detection;

5. Estimated life expectancy of at least 8 weeks;

6. Eastern Cooperative Oncology Group (ECOG) performance status ≤ 2;

7. Significant toxicities incurred as a result of previous anti-cancer therapy resolved
to ≤ Grade 1 (NCI-CTCAE version 4.03);

8. Acceptable laboratory values at screening;

9. Male patients must agree to use an adequate and medically accepted method of
contraception throughout the study and for at least 6 months after if their sexual
partners are women of child bearing potential (WOCBP).

10. WOCBP must be using highly effective and medically accepted method of contraception to
avoid pregnancy throughout the study and for at least 6 months after the study ;

11. WOCBP must have a negative serum or urine pregnancy test within 72 hours prior to the
start of study drug.

12. Peripheral blast count Day 1.

Exclusion Criteria:

1. Diagnosis of chronic myelogenous leukemia in blast crisis;

2. Prior hematopoietic stem cell transplantation;

3. Cancer chemotherapy within four weeks prior to start of MCLA-117;

4. Previous treatment with radiotherapy, or immunotherapeutic agents, or receipt of live
vaccines in the 4 weeks prior to study drug administration;

5. Previous treatment with any other investigational agents within 4 weeks prior to
MCLA-117 administration;

6. Concurrent need of use of corticosteroids > 10 mg/day of oral prednisone or the
equivalent, except topical preparations (e.g., topical creams, steroid inhaler, nasal
spray or ophthalmic solution);

7. Use of immunosuppressant medications within 4 weeks of MCLA-117 administration;

8. Clinically active central nervous system (CNS) leukemia;

9. Patients who are pregnant or lactating;

10. Patients with an active infection or with an unexplained fever during screening or on
the first scheduled day of dosing;

11. Patients with known hypersensitivity to any of the components of MCLA-117 or who have
had prior hypersensitivity reactions to human or humanized monoclonal antibodies;

12. Patients with known HIV, hepatitis B or C;

13. Patients with New York Heart Association Class III or IV congestive heart failure or
left ventricular ejection fraction (LVEF) < 50%, or significant uncontrolled cardiac
disease, current diagnosis of unstable angina, uncontrolled congestive heart failure,
new myocardial infarction, or ventricular arrhythmia requiring medication;

14. Prior malignancy (other than basal cell carcinoma and cervical in situ carcinoma)
unless treated with a curative intend and without evidence of malignant disease for 1
year before screening. Patients with prior hematologic malignancies that have
progressed to AML (such as Myelodysplastic syndrome, myeloproliferative neoplasms,
bi-phenotypic leukemias, AcuteLymphocyticLeukemia) or AML that has relapsed are
eligible;

15. Urinary protein >2+ possibly indicative of renal disease. If the 24 hours urine
protein shows a result of < 100 mg protein, subject can be eligible;

16. Patients with any other medical or psychological condition deemed by the Investigator
to be likely to interfere with a patient's ability to sign informed consent, cooperate
and participate in the study, or interfere with the interpretation of the results;

17. WOCBP or males with a WOCB partners not willing to use highly effective and medically
accepted methods of contraception for 6 months after last study drug administration.

18. Need for concurrent other cytoreductive chemotherapy.