SL-401 in Advanced, High Risk Myeloproliferative Neoplasms (Systemic Mastocytosis, Advanced Symptomatic Hypereosinoophic Disorder, Myelofibrosis, Chronic Myelomonocytic Leukemia)

Inclusion Criteria:

All Patients (Stages 1 and 2):

1. The patient is ≥18 years old
2. The patient has an Eastern Cooperative Oncology Group (ECOG) performance score of 0-2

3. The patient has adequate baseline organ function, including cardiac, renal, and hepatic function:

   • Left ventricular ejection fraction (LVEF) ≥ institutional lower limit of normal as measured by multigated acquisition scan or 2-dimensional (2-D) echocardiogram within 28 days prior to start of therapy and no clinically significant abnormalities on a 12-lead electrocardiogram (ECG)
   • Serum creatinine ≤1.5 mg/dL (or ≤114 µmol/L)
   • Serum albumin ≥3.2 g/dL (or ≥32 g/L) in the absence of receipt of (IV) albumin within the previous 72 hours
   • Bilirubin ≤1.5 mg/dL (or ≤26 µmol/L)
   • Aspartate transaminase (AST) and alanine transaminase (ALT) ≤2.5 times the upper limit of normal (ULN)
   • CPK ≤2.5 times the ULN
4. If a woman of child bearing potential, the patient has a negative serum or urine pregnancy test within 1 week prior to SL-401 treatment (intervals shorter than 1 week are acceptable, if required by institutional guidelines)
5. The patient has signed informed consent prior to initiation of any study-specific procedures or treatment
6. The patient is able to adhere to the study visit schedule and other protocol requirements, including follow-up for response assessments
7. The patient agrees to use acceptable contraceptive methods for the duration of time in the study, and to continue to use acceptable contraceptive methods for 2 months after the last SL-401 infusion
8. Patient has an absolute neutrophil count (ANC) ≥0.5×10⁹/L

Additional Inclusion Criteria Specific to Patients with MF and CMML (Stages 1 and 2)

Exclusion Criteria:

All Patients (Stages 1 and 2):

1. Patient has persistent clinically significant toxicities Grade ≥2 from previous chemotherapy not readily controlled by supportive measures (excluding alopecia, nausea, and fatigue)
2. Patient has received treatment with chemotherapy, wide-field radiation, or biologic therapy within 14 days of study entry
3. Patient has received treatment with another investigational agent within 14 days of study entry or concurrent treatment with another investigational agent.
4. Patient has previously received treatment with SL-401 or has a known hypersensitivity to any components of the drug product
5. Patient has an active malignancy and/or cancer history (excluding myeloproliferative disorders and concomitant myeloid malignancies as specified in the inclusion criteria) that can confound the assessment of the study endpoints. Patients with a past cancer history (within 2 years of entry) and/or ongoing active malignancy or substantial potential for recurrence must be discussed with the Sponsor before study entry. Patients with the following neoplastic diagnoses are eligible: non-melanoma skin cancer, carcinoma in situ (including superficial bladder cancer), cervical intraepithelial neoplasia, or organ-confined prostate cancer with no evidence of progressive disease
6. Patient has clinically significant cardiovascular disease (e.g., uncontrolled or any New York Heart Association Class 3 or 4 congestive heart failure, uncontrolled angina, history of myocardial infarction or stroke within 6 months of study entry, uncontrolled hypertension or clinically significant arrhythmias not controlled by medication)
7. Patient has uncontrolled, clinically significant pulmonary disease (e.g., chronic obstructive pulmonary disease, pulmonary hypertension) that, in the Investigator's opinion, would put the patient at significant risk for pulmonary complications during the study
8. Patient has known active or suspected disease involvement of the central nervous system (CNS). If suspected due to clinical findings, CNS disease should be ruled out with relevant imaging and/or examination of cerebrospinal fluid
9. Patient is receiving immunosuppressive therapy, with the exception of corticosteroids as specified in the inclusion criteria and tacrolimus, for treatment or prophylaxis of graft-versus-host disease (GVHD). If the patient has been on immunosuppressive treatment or prophylaxis for GVHD, the treatment(s) must have been discontinued at least 14 days prior to study drug and there must be no evidence of Grade ≥2 GVHD
10. Patient has uncontrolled intercurrent illness including, but not limited to, uncontrolled infection, disseminated intravascular coagulation, or psychiatric illness that would limit compliance with study requirements
11. Patient is pregnant or breast feeding
12. Patient has known human immunodeficiency virus (HIV)
13. Patient has evidence of active or chronic Hepatitis B or Hepatitis C infection.
14. Patient is oxygen-dependent
15. Patient has any medical condition that in the Investigator's opinion place the patient at an unacceptably high risk for toxicities

Additional Exclusion Criteria Specific to Patients with MF and CMML (Stages 1 and 2)