A Trial of PF-07901800 (TTI-621) for Patients With Hematologic Malignancies and Selected Solid Tumors

A Phase 1a/1b Dose Escalation and Expansion Trial of TTI-621, a Novel Biologic Targeting CD47, in Subjects With Relapsed or Refractory Hematologic Malignancies and Selected Solid Tumors

Multicenter, open-label, phase 1a/1b trial of PF-07901800 (TTI-621) in subjects with relapsed or refractory hematologic malignancies and selected solid tumors.

This is a trial of PF-07901800 (TTI-621) in subjects with relapsed or refractory hematologic malignancies and selected solid tumors.

TTI-621 (SIRPαFc) is a soluble recombinant fusion protein created by directly linking the sequences encoding the N-terminal CD47 binding domain of human SIRPα with the Fc domain of human immunoglobulin (IgG1). TTI-621 acts by binding human CD47 and preventing it from delivering an inhibitory "do not eat" (anti phagocytic) signal to macrophages.

This trial will be conducted in 2 phases and 4 parts: Phase 1a Part 1 (escalation phase) and Phase 1b Parts 2-4 (expansion phase).

In the dose Escalation Phase (phase 1a Part 1), subjects with lymphoma will be enrolled in sequential dose cohorts to receive TTI-621 to characterize safety, tolerability, pharmacokinetics, and the maximum-tolerated dose (MTD).

In the Expansion Phase (phase 1b Parts 2-4), TTI-621 will be given to subjects with a variety of hematologic malignancies and selected solid tumors to further define safety and to characterize efficacy. In the Expansion Phase Part 2, the safety and efficacy of TTI-621 will also be assessed when it is given in combination with other anti-cancer drugs. The dose of TTI-621 to be delivered in the Expansion Phase Parts 2-3 of the study may be increased or decreased based on the subject's tolerability and on the subject's response to treatment.

In the phase 1b dose optimization of the study (Part 4), further dose escalation of TTI-621, beyond the dose determined during phase 1a dose escalation, will be pursued in patients with relapsed and/or refractory CTCL following a 3+3 escalation design and using a revised DLT criteria to further evaluate the safety and tolerability of TTI-621 at dose levels higher than the initially recommended phase 1b Parts 2-3.

Secondary objectives include further characterization of the pharmacokinetics, pharmacodynamics, and development of ADA; and to gain preliminary evidence of the anti-tumor activity of TTI-621 in subjects with a variety of hematologic malignancies and selected solid tumors. In addition, the safety of TTI-621 will be evaluated in combination with other anti-cancer agents.

Pfizer decided terminating this study for administrative reasons on 22Mar2022 (stopping enrollment as of 15Apr2022). The decision wasn't due to safety concerns or requests from regulatory authorities.

MAJOR ELIGIBILITY CRITERIA:

Phase 1a Escalation

• Histologically documented, measurable, advanced lymphomas, transfusion-independence

Phase 1b Expansion (Part 2 and 3) • Advanced malignancy: IBCL, ABCL, cHL, AML, ALL, MDS, MPN, SCLC, PTCL and CTCL; measurable disease who have relapsed or are refractory following at least 2 prior systemic therapeutic attempts (1 prior systemic attempt for PTCL). For CTCL, extracorporeal photochemotherapy (ECP) considered a systemic therapy. Local radiation and topical agents are not systemic therapies.

Phase 1b dose optimization (Part 4)

• Histologically confirmed diagnosis of CTCL (both Mycosis Fungoides and Sezary Syndrome): Failed at least 2 prior systemic therapies for CTCL (Systemic therapy does not include local radiation therapy or topical agents); History of histologically documented diagnosis of CTCL stage IB to IVB

Inclusion Criteria (all subjects):

• Advanced measurable malignancy with previously progressed on, or currently progressing on standard anticancer therapy or for whom no other approved conventional therapy exists
• Eastern Cooperative Oncology Group (ECOG) 0-2
• Adequate hematologic, hepatic, renal, and coagulation function; fresh or archived tumor tissue available for immunohistochemistry
• Recovery from prior treatments and/or surgeries; no history of hemolytic anemia or bleeding diathesis.
• AML M3 (French American British, FAB, classification) (i.e., acute promyelocytic leukemia [APL]) excluded

Exclusion Criteria:

• Known current central nervous system disease involvement or untreated brain metastases
• Allogeneic transplant within 30 days prior to the planned start of treatment or subjects with active graft-vs-host disease with the exception of Grade 1 skin involvement
• History of hemolytic anemia or bleeding diathesis