Currently, the number of days required to mobilize and collect a patient’s or donor’s stem cells is a minimum of five days in blood cancer patients and healthy donors and as many as 30 days or more in patients with sickle cell disease. When planning for a patient’s transplant, transplanting physicians cannot reliably predict at the outset how long it will take for patients to mobilize the number of cells required. Many patients require multiple collections, including approximately 40% of blood cancer patients and 75% of sickle cell disease patients. In addition, each day scheduled for attempted mobilization and collection can cause an accumulation of both the direct costs associated with the repeated use of mobilization agents and other healthcare resources, including personnel time, and the indirect costs associated with the need to block time in the limited number of chairs in transplant centers that are used to collect stem cells. Similarly,
HSC-based
gene therapies could benefit from more efficient collection of stem cells which could potentially reduce gene therapy manufacturing timelines and costs. Additionally, there are no approved mobilization options for patients with sickle cell disease and autoimmune diseases, and the
off-label
use of currently available medicines is associated with significant safety risks including vaso-occlusive events in sickle cell disease patients.
Magenta is
developing MGTA-145 as
a new first-line standard of care for stem cell mobilization in a broad range of diseases, for both autologous and allogeneic
transplants. MGTA-145, a
CXCR2 agonist, works in combination with plerixafor, a CXCR4 antagonist, to harness a complementary physiological mechanism for stem cell mobilization. The goal
of MGTA-145 is
to be the preferred first-line mobilization option for all patients and donors through rapid, reliable, predictable and safe mobilization and collection of high numbers of functional stem cells. In 2020, we completed a Phase 1 clinical trial in healthy volunteers to evaluate the ability of
MGTA-145,
in combination with plerixafor, to mobilize stem cells. Based on the results of the study, we have advanced the program into three ongoing and planned Phase 2 clinical trials, including an autologous transplant trial in multiple myeloma patients; an allogeneic transplant trial with healthy donor cells collected for transplant in patients with acute myeloid leukemia, myelodysplastic syndromes or acute lymphocytic leukemia, or ALL; and lastly, a planned trial in partnership with bluebird bio, Inc. to mobilize and collect the stem cells of sickle cell disease patients.
In addition to the opportunity to address the challenges in mobilization and collection of stem cells, Magenta also seeks to improve patient conditioning prior to transplant. Conditioning is the process by which patients are treated with chemotherapy prior to transplant to ensure that the bone marrow has sufficient space to receive newly transplanted stem cells. Currently, only approximately 50% of eligible patients receive a stem cell transplant, in part because of the risks and toxicities of the chemotherapeutic agents available today.
Magenta is developing a suite of novel antibody drug conjugates, or ADCs, for conditioning, a step in the transplant process that currently relies on the use of systemic chemotherapy agents and radiation. We are seeking to replace these
toxic, non-targeted conditioning
agents with targeted ADCs.
Magenta’s lead conditioning program,
MGTA-117,
is designed to selectively deplete stem cells and reduce the need for high-dose or high-intensity chemotherapeutic agents in oncology applications and potentially eliminate the use of busulfan in gene therapy applications.
MGTA-117 targets
CD117, which is highly expressed on the cell surface of HSCs and leukemia cells, making it an ideal target for conditioning across broad sets of diseases, including certain blood cancers, hemoglobinopathies (sickle cell disease and beta-thalassemia) and inherited metabolic disorders.
Our additional research-stage conditioning programs target stem and/or immune cells and are being designed to eliminate toxic chemotherapy conditioning regimens across multiple disease settings. Our C100 program focuses on addressing opportunities in immune reset for autoimmune diseases. Our C300 program is being designed to provide for lymphodepletion prior to cell therapies such as chimeric antigen receptor T cells, or
CAR-T.
Magenta is also evaluating two programs with potential in cell therapy. Each is a small molecule used to manufacture a high number of functional stem cells, from either a donor or gene-modified stem cells from a patient.
MGTA-456
is a cell therapy designed to generate higher cell doses that are well matched to the patient, which has been shown to improve the speed and success of engraftment in stem cell transplant and improve disease outcomes. In June 2020, we announced that we discontinued enrollment in our Phase 2 trial of
MGTA-456
in inherited metabolic diseases. Enrollment in an investigator-initiated trial in patients with blood cancers has been completed, and we plan to use these data, when available, to inform a decision regarding future program development in blood cancers. Our second cell therapy program, E478, is a small molecule aryl hydrocarbon receptor, or AHR, antagonist which
uses the same mechanism used to manufacture
MGTA-456
to expand gene-modified HSCs for stem cell-based gene therapy and genome editing.
Magenta intends to become a fully integrated discovery, development and commercial company in the field of stem cell transplant. We are developing our product candidates to be used individually or, in some cases, in combination with each other. As a result, our portfolio could be tailored to the patient’s disease, such that a patient may receive more than one Magenta therapy as part of his or her individual stem cell transplant.