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Our Clinical Trial

We have initiated VBP101, our first-in-human Phase 1/2a trial of trem-cel (formerly VOR33) in combination with Mylotarg™

The VBP101 trial is actively enrolling patients. This trial will provide important validating evidence of the potential of trem-cel and our broader engineered Hematopoietic Stem Cell (eHSC) approach. We plan to initially evaluate engraftment and tolerability, then preliminarily assess clinical activity in the second part of the trial.

Study goals

The primary goals of the VBP101 trial are to evaluate tolerability and feasibility, with a focus on confirming that trem-cel can engraft in patients in a timely manner. Patients will then be eligible for subsequent treatment with Mylotarg. We will examine the incidence of hematopoietic toxicities associated with Mylotarg in patients engrafted with trem-cel. Any observed protection from such on-target toxicity in this Phase 1/2a trial would serve as an important proof of principle for our research and development platform. While this trial is not powered to confirm significance of efficacy, relapse-free survival and overall survival will be assessed.

Enrollment & follow-up

The VBP101 trial (NCT04849910) is open to AML patients who are at high risk of relapse and undergoing myeloablative hematopoietic stem cell transplant (HCT). Participants (18-70 years old) must have a diagnosis of CD33+ AML, an HLA-matched related or unrelated (10/10) donor and be a candidate for myeloablative HCT. Additional key inclusion criteria include morphologic remission with intermediate/poor cytogenetics and the presence of minimal residual disease. Patients with 5-10% bone marrow-only blasts with any cytogenetic risk are also eligible. Key exclusion criteria include prior auto/allo-HCT or treatment with Mylotarg.

To administer trem-cel, HSCs from matched healthy donors will be mobilized and isolated from peripheral blood, engineered into trem-cel and then introduced into patients following myeloablative conditioning. As a safety measure, we will freeze and preserve a portion of the original donor cells to use in case of the failure of trem-cel to engraft.

At day 60, we will re-evaluate patients for disease status and peripheral blood counts. Those patients remaining in remission and meeting dosing criteria will be treated with maintenance doses (escalated in separate dosing cohorts) of Mylotarg once a month for four months to potentially reduce the risk of relapse by killing residual AML cells. Patients in early relapse may be treated with salvage therapies including Mylotarg. Patients will be followed up for two years after HCT and for up to 15 years post-HCT in a separate long-term follow-up study.


We expect the key analytical and clinical read-outs of the VBP101 clinical trial to include the following:


Incidence of patients who achieve neutrophil engraftment (first day of 3 consecutive days of absolute neutrophil count (ANC) ≥500 cells/mm3) by Day 28.

Mylotarg toxicities

Patients receiving Mylotarg usually exhibit significant myelosuppression within one to two weeks following dosing. Patients will be monitored for neutrophil cell counts following Mylotarg dosing, and will be assessed for suitability for receiving repeat Mylotarg dosing.

Transplant Outcomes

Standard measures of transplant safety and efficacy will be reported including; Incidence of graft failure, transplant-related mortality, graft vs. host disease and time to neutrophil and platelet engraftment.

Clinical activity observations

Following Mylotarg treatment, patients will be monitored for the presence of MRD, which are biomarkers in bone marrow indicating remaining presence of cancer. MRD positivity is a strong predictor of AML relapse, and change from MRD positive to negative status would be clinically meaningful. In addition, patients will be assessed for the incidence of relapse-free survival and overall survival.

To learn more about our clinical trial, VBP101, please see our listing:

Allogeneic Engineered Hematopoietic Stem Cell Transplant (HCT) Lacking the CD33 Protein, and Post-HCT Treatment With Mylotarg, for Patients With CD33+ AML

If you have questions, please contact us.

The science behind the Vor Bio platform

We are applying proven technologies in new ways by genetically modifying healthy donor HSCs for protection and enabling use of modalities such as ADCs and CAR-Ts post-transplant.