anti cd19 anti cd22 bispecific immunotoxin dt2219arl

Drug Overview

The medication known as anti cd19 anti cd22 bispecific immunotoxin dt2219arl (also identified as OXS-1550) is an investigational, next-generation targeted therapy designed to treat aggressive B-cell malignancies, such as Acute Lymphoblastic Leukemia (ALL) and Non-Hodgkin Lymphoma (NHL). It belongs to a specialized class of drugs called bispecific ligand-directed toxins (BLTs).

Unlike traditional chemotherapy, which circulates through the entire body, DT2219ARL acts like a “molecular Trojan Horse.” It is engineered to simultaneously recognize two distinct markers on the surface of B-cells: CD19 and CD22. By targeting two receptors at once, the drug is more likely to find and attach to cancer cells even if one of the receptors is “hidden” or lost, a common way cancer develops resistance.

• Generic Name: DT2219ARL.
• Other Names: OXS-1550, anti-CD19/CD22 BLT DT2219ARL.
• Drug Class: Bispecific Recombinant Immunotoxin.
• Payload: Diphtheria Toxin (DT390).
• Route of Administration: Intravenous (IV) infusion.
• FDA Approval Status: Investigational. As of March 2026, DT2219ARL is not FDA-approved. It has completed Phase I and Phase I/II clinical trials (NCT02370160). It has been granted Orphan Drug Designation by the FDA for the treatment of both ALL and NHL, but it is not yet available for general clinical use.

What Is It and How Does It Work? (Mechanism of Action)

The Bispecific Advantage

Most targeted therapies only look for one protein (like CD19). Cancer cells often stop producing that protein to “evade” the drug. DT2219ARL targets both CD19 and CD22, which are almost always present on B-cell leukemia and lymphoma cells. Targeting two receptors increases the “binding avidity”—essentially, the drug “sticks” to the cancer cell much more tightly.

Molecular Level Mechanisms

1. Selective Binding: The drug circulates until it finds a B-cell expressing CD19, CD22, or both. It binds to these receptors using specialized “scFv” ligands.
2. Internalization: Once bound, the cancer cell “swallows” the drug (endocytosis).
3. Toxin Activation: Inside the cell, the payload—a truncated version of diphtheria toxin (DT390)—is released into the cell’s interior (cytoplasm).
4. ADP-Ribosylation: The toxin catalyzes a chemical reaction that disables Elongation Factor 2 (EF-2). EF-2 is the “engine” the cell uses to build proteins.
5. Irreversible Inhibition: Because one single molecule of diphtheria toxin can disable thousands of EF-2 proteins, the cell’s ability to make proteins is completely and permanently shut down.
6. Apoptosis: Without the ability to make proteins, the cancer cell enters apoptosis (programmed cell death).

FDA Approved Clinical Indications

There are currently no FDA-approved clinical indications for DT2219ARL.

It is strictly available through participation in research studies. It has been primarily investigated for:

• Relapsed or Refractory B-lineage Acute Lymphoblastic Leukemia (ALL): For patients who have failed multiple prior lines of chemotherapy or stem cell transplants.
• Relapsed or Refractory B-cell Non-Hodgkin Lymphoma (NHL): Including aggressive subtypes like Burkitt’s lymphoma.
• Chronic Lymphocytic Leukemia (CLL): Investigated as a potential therapy for resistant B-cell cases.

Dosage and Administration Protocols

Because this agent is investigational, there is no “standard” clinical dose. The following information is based on the protocols used during its Phase I/II dose-escalation and expansion trials.

Clinical Efficacy and Research Results

Clinical data from its Phase I and II trials (NCT00889408 and NCT02370160) provided significant insights into its potential.

• Response in ALL: Early Phase I/II results showed that approximately 75% of ALL patients (3 out of 4 in an early cohort) exhibited a clinical benefit, including some complete remissions.
• MRD Negativity: Some responders achieved Minimal Residual Disease (MRD) negativity, meaning no detectable leukemia cells remained in the bone marrow.
• Superiority to Monospecifics: Preclinical research confirmed that DT2219ARL was significantly more effective than using individual drugs that targeted only CD19 or CD22 alone.
• Neutralizing Antibodies: A major challenge in immunotoxin therapy is that the body can “recognize” the diphtheria toxin as foreign and build an immune defense against it. However, clinical studies showed a surprisingly low incidence of these neutralizing antibodies (only ~30%).

Safety Profile and Side Effects

As an immunotoxin, DT2219ARL has a very specific set of side effects that differ from standard chemotherapy. These are largely related to the “leaking” of blood vessels, a known risk with toxin-based therapies.

Common Side Effects (>20%):

• Hypoalbuminemia: A drop in the level of albumin protein in the blood.
• Weight Gain: Often due to fluid retention.
• Transaminitis: Temporary elevation of liver enzymes (ALT/AST).
• Fever: Usually mild and transient after the infusion.

Serious Adverse Events (Grade 3 or Higher):

• Capillary Leak Syndrome (CLS): This is the most serious risk. The drug can cause small blood vessels to become “leaky,” leading to swelling, low blood pressure, and fluid buildup around the lungs or heart.
• Hepatotoxicity: Significant liver stress requiring dose interruption.
• Thrombocytopenia: A drop in platelet counts, increasing the risk of bruising.
• Management Strategies: To manage CLS, patients are often given IV fluids and monitored very closely for weight gain and changes in blood pressure. Albumin infusions may be used to counteract leakage.

Research Areas

In Stem Cell and Regenerative Medicine, DT2219ARL is studied for its role in “Niche Clearance.” Before a patient receives a bone marrow transplant, all cancer cells must be removed from the “niche” (the space where blood cells grow). Researchers are investigating if DT2219ARL can be used to “clean” the bone marrow of leukemia stem cells more effectively than radiation, allowing the new healthy stem cells to regenerate the blood system more successfully.

Patient Management and Practical Recommendations

Pre-treatment Tests:

• CD19 and CD22 Expression Testing: A bone marrow biopsy or flow cytometry must confirm the cancer cells have the target proteins.
• Baseline Liver and Kidney Function: To ensure the body can safely process the drug.
• Baseline Weight and Albumin: To monitor for signs of Capillary Leak Syndrome.

Precautions:

• Fluid Monitoring: Patients must be weighed daily during treatment; a sudden gain of 2-3 pounds can be an early sign of CLS.
• Immune Response: Because the drug uses a bacterial toxin, doctors watch for allergic reactions during the first infusion.

“Do’s and Don’ts” List:

• DO report any “puffiness” in the face or ankles or shortness of breath immediately.
• DO keep track of your daily temperature; a fever is common but needs to be evaluated.
• DON’T ignore sudden dizziness, as it could be a sign of low blood pressure from vessel leakage.
• DON’T skip follow-up blood work, as liver enzymes and albumin levels must be tracked to ensure safety.

Legal Disclaimer

The information provided is for educational purposes only and does not constitute medical advice. DT2219ARL is an investigational agent and is not approved by the US FDA for general use. It is available only through participation in clinical trials. Always consult with a qualified hematologist-oncologist regarding currently available treatments and eligibility for active research studies.