Study of APVO436 in Patients With AML or MDS

Part 1 - Dose Escalation: Dosing will start at the minimum anticipated biologic effect level (MABEL) in single-patient cohorts for the first 3 dose cohorts up to and including 3 mcg. Patients enrolled will have either: 1) relapsed or refractory AML and refuse or are not eligible for intensive chemotherapy or an allogeneic stem cell transplant, or 2) relapsed or refractory MDS and have \> 5% blasts in the marrow or any circulating blasts in the peripheral blood and have failed a prior hypomethylating agent (HMA); failure is defined as intolerance to HMA, lack of response (no CR by at least 6 cycles), or have IWG defined progressive disease during or after treatment with an HMA. In single-patient Cohorts 1 to 3, the next dose cohort will only enroll after the patient in the current dose cohort has completed the first cycle of dosing (4 weeks) and no Grade ≥ 2 adverse events (AEs) (hematologic or non-hematologic) have occurred. If any Grade ≥ 2 AE occurs in the single-patient cohorts, then that cohort and all subsequent single-patient cohorts will be expanded to a 3 + 3. The next dose cohort in the 3 + 3 cohorts (all cohorts beyond Cohort 4) is started after patients in the previous dose cohort have completed the first cycle of dosing and an evaluation of AEs for DLTs during the DLT observation period has been completed. For the first 2 patients within each dose cohort, administration of the first dose must be separated by a minimum of 36 hours. At the conclusion of each cycle, patients with significant cytopenias without evidence of leukemia will have the dose delayed. Beginning in Cohort 5, and for all cohorts going forward, stepped dosing will be introduced to mitigate against the development of infusion-related reactions and cytokine release syndrome. Patients will receive APVO436 intravenously for six 28 day cycles, unless disease progression, intolerable toxicity, or withdrawal of consent occurs earlier. There is an option for longer treatment if the patient is responding. The RP2D level will be based on clinical activity, safety, incidence of DLTs, PK, and PD in each dose cohort. Part 2 - Dose Expansion: The MTD for APVO436 was not reached at a dose level of 240 µg/cycle (Cohort 10 in the dose escalation phase). The sub-MTD dose level of Cohort 6A was identified as the RP2D level of APVO436 for further evaluation during the expansion phase. In the open-label, multi-center, dose expansion phase of the study (Part 2), a total of 90 primary AML patients will be enrolled into 5 cohorts of 18 patients each. The goal of this expansion phase of the study is to evaluate the safety and tolerability of APVO436 at the RP2D level when it is used as an adjunct to the standard of care and obtain a preliminary assessment of the anti-leukemia activity of APVO436-containing experimental monotherapy and combination therapy modalities. In Cohorts 1-4, APVO436 will be administered at a fixed dosage of 18 mcg after a weekly ramp up during Cycle 1 (Cohorts 1, 3, 4) or Cycle 1-2 (Cohort 2). In Cohort 5, APVO436 will be administered at a fixed dose of 18 mcg twice weekly after a weekly ramp up during Cycle 1. The specific patient populations and experimental treatments for the expansion phase are as follows: Cohort 1. Induction with Chemotherapy (ChT) plus APVO436. 1st or 2nd Early Relapse. Patients may receive either Ara-C intermediate dose (IDAC) or MEC as the ChT backbone. Fit primary or secondary AML patients (Age: \>18 years) in 1st or 2nd relapse with last CR \<12 months or primary refractory disease will receive 4 x 28-day cycles of combined 2-drug immunochemotherapy: APA \[APVO436+Intermediate dose ARA-C (IDAC) or APMEC \[APVO436+MEC\]. Cohort 2. Induction with APVO436 + Venetoclax + Azacitidine - Frontline or 1st Relapse. Poor prognostic but fit primary or secondary AML patients (Age \>18 years) who are treatment-naïve or in 1st relapse will receive 4 x 28-day cycles of combined 3-drug immunochemotherapy: APVA \[APVO436+Venetoclax+Azacitidine\]. Cohort 3: Consolidation post 7+3 - Frontline + 1st Relapse. Fit primary AML patients (Age: \>18 years) with FLT3-negative intermediate or adverse risk AML (including but not limited to: TP53, RUNX1 and ASXL1 mutations and/or complex cytogenetics) who are treatment-naïve or in 1st relapse with a duration of CR1\<1 year will receive 4 x 28-day cycles of immunotherapy with APVO436 after hematologic recovery (ANC\>1,000/µL; Hgb ≥9 g/dL; Plt≥100,000/µL) post induction. Cohort 4: MRD-positive (MRD+) 1st Remission, APVO436 + Azacitidine combination. \>18 years old MRD+ (at ≥0.1% level by multicolor-multiparameter flow cytometry \[MFC\] in Central Lab) high-risk 1st remission AML patients will be treated with 4 x 28-day cycles of APVO436 + oral azacitidine (Onureg, CC-486). Cohort 5: MRD+ 2nd Remission, Single Agent APVO436. \>18 years old MRD+ (at ≥0.1% level by MFC in Central Lab) AML patients who are in 2nd remission post-induction with a standard of care regimen will be treated with 4 x 28-day cycles of APVO436 monotherapy.