Last reviewed 2026-05-23 · How we verify

Molecule 129 (TAGRAXOFUSP)

Molecule 129 (generic name: TAGRAXOFUSP) is a CD123 Interaction [EPC] Recombinant protein drug developed by Stemline Therapeeutics Inc. It is currently FDA-approved (first approved 2018) for Blastic Plasmacytoid Dendritic Cell Neoplasm (BPDCN).

Tagraxofusp works by binding to CD123 on cancer cells, causing them to die.

Molecule 129, also known as Elzonris, is a binding agent that targets the Interleukin-3 receptor subunit alpha. It is classified as a protein modality and works by binding to this receptor subunit.

At a glance

Mechanism of action

Tagraxofusp-erzs is CD123-directed cytotoxin composed of recombinant human interleukin-3 (IL-3) and truncated diphtheria toxin (DT) fusion protein that inhibits protein synthesis and causes cell death in CD123-expressing cells.

Approved indications

• Blastic Plasmacytoid Dendritic Cell Neoplasm (BPDCN)

Boxed warnings

• WARNING: CAPILLARY LEAK SYNDROME Capillary Leak Syndrome (CLS) which may be life-threatening or fatal, can occur in patients receiving ELZONRIS. Monitor for signs and symptoms of CLS and take actions as recommended [see Warnings and Precautions ( 5.1 )] . WARNING: CAPILLARY LEAK SYNDROME See full prescribing information for complete boxed warning. Capillary Leak Syndrome (CLS), which may be life-threatening or fatal if not properly managed, can occur in patients receiving ELZONRIS. ( 5.1 )

Common side effects

• Capillary leak syndrome
• Nausea
• Fatigue
• Peripheral edema
• Pyrexia
• Weight increase
• Hypotension
• Hypertension
• Constipation
• Vomiting
• Diarrhea
• Decreased appetite

Key clinical trials

• A Study of Tagraxofusp in Combination With Venetoclax and Azacitidine in Adults With Untreated CD123+ Acute Myeloid Leukemia Who Cannot Undergo Intensive Chemotherapy (PHASE2)
• Tagraxofusp and Azacitidine for Maintenance Treatment in Patients With CD123 Positive AML and MDS Following Donor Hematopoietic Cell Transplant (PHASE1)
• Venetoclax, SL-401, and Chemotherapy for the Treatment of Blastic Plasmacytoid Dendritic Cell Neoplasm (PHASE2)
• A Multi-Site Break Through Cancer Trial: Targeting Measurable Residual Disease in Patients With Acute Myeloid Leukemia: A Phase 1/2 Study of Tagraxofusp, Azacitidine, and Venetoclax (PHASE1,PHASE2)
• Tagraxofusp and Azacitidine With Venetoclax in Newly Diagnosed Secondary AML After Hypomethylating Agents (PHASE2)
• Phase I/II Study of Tagraxofusp in Combination With Decitabine for Patients With Myelomonocytic/Myeloproliferative Neoplasm and High Risk Myelodysplastic Syndromes (PHASE1,PHASE2)
• Phase II Study Evaluating the Efficacy and Safety of the Combination of Tagraxofusp and Venetoclax in Treatment-naive Blastic Plasmacytoid Dendritic Cell Neoplasm Patients (PHASE2)
• SL-401 in Combination With Azacitidine or Azacitidine/Venetoclax in Acute Myeloid Leukemia (AML), High-Risk Myelodysplastic Syndrome (MDS) or Blastic Plasmacytoid Dendritic Cell Neoplasm (BPDCN) (PHASE1)

Primary sources

Every claim on this page is sourced from regulatory or scientific primary sources. See our editorial policy for full methodology.

Competitive intelligence

For the full competitive landscape — auto-detected comparators, recent regulatory actions across the set, upcoming PDUFA, patent timeline, sponsor landscape:

• Molecule 129 CI brief — competitive landscape report
• Molecule 129 updates RSS · CI watch RSS
• Stemline Therapeeutics Inc portfolio CI

Frequently asked questions about Molecule 129

Related

• Drug class: All CD123 Interaction [EPC] drugs
• Target: All drugs targeting Elongation factor 2
• Manufacturer: Stemline Therapeeutics Inc — full pipeline
• Therapeutic area: All drugs in Oncology
• Indication: Drugs for Blastic Plasmacytoid Dendritic Cell Neoplasm (BPDCN)

Primary sources · FDA · ClinicalTrials.gov · EMA · SEC EDGAR · ChEMBL · Wikidata · full sourcing