LOP628 is an antibody-drug conjugate (ADC) consisting of an anti-cKit humanized IgG1/κ antibody conjugated to a maytansine payload via a non-cleavable linker.

LOP628 provides an opportunity to target cKit overexpressing tumors.

Inclusion Criteria:

For patients with solid tumors:

• documented cKit-positive neoplasms
• Patient must have progressive disease as defined by any of the following:
• SCLC: patient has progressed after at least 1 prior therapy
• GIST : patient has relapsed or has refractory disease, and no further approved effective therapeutic option exists
• Patients with other cKit-positive solid tumors: patient has progressed after at least one prior line of therapy and no further approved effective therapeutic option exists
• Patient has measurable disease as per RECIST v1.1 criteria

For patients with AML:

• documented cKit-positive acute myelogenous leukemia
• Consent to newly obtained bone marrow aspirate
• Patient must have progressive disease defined as relapsed or refractory non-PML AML following standard therapy or for whom no effective therapy exists.
• Blast count < 50,000/mm3

Exclusion Criteria:

For patients with solid tumors:

• Patient has central nervous system (CNS) metastatic involvement unless the CNS metastases have been previously treated and the patient is clinically stable and on a stable dose of corticosteroids for at least 4 weeks prior to enrollment.
• Patient has the presence of other clinically significant hematologic, cardiac, respiratory, gastrointestinal, renal, hepatic or neurological conditions.
• Patient has a history of serious allergic reactions, which in the opinion of the investigator may pose an increased risk of serious infusion reactions
• Patient has been previously treated with cKit directed antibodies
• Pregnant or nursing women

For patients with AML:

• Patient has received prior allogeneic bone marrow transplant (BMT).
• Patient has the presence of other clinically significant cardiac, respiratory, gastrointestinal, renal, hepatic or neurological disease
• Patient has a history of serious allergic reactions, which in the opinion of the investigator may pose an increased risk of serious infusion reactions
• Patient has been previously treated with cKit directed antibodies
• Pregnant or nursing women