Tambiciclib
An investigational treatment for Acute Myeloid Leukemia.
The same compound appears under different names depending on the context. Here is how to identify Tambiciclib wherever you encounter it, plus the key facts at a glance.
- Generic name
- Tambiciclib
- Development codes
- SLS009, GFH009
- Drug class
- CDK9 inhibitor
- Manufacturer
- SELLAS Life Sciences
- How it's taken
- IV infusion (investigational), with venetoclax and azacitidine
An investigational IV drug being tested with venetoclax and azacitidine, first in people whose AML came back after venetoclax and now in an 80-patient Phase 2 study of newly diagnosed AML, with topline results expected in the fourth quarter of 2026. It holds FDA Rare Pediatric Disease Designations for pediatric AML and pediatric ALL. It is not FDA approved.
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Where Tambiciclib fits
One of several add-ons to venetoclax and azacitidine in trials. Its distinct angle is the group that relapses on or resists venetoclax, for which no targeted option exists unless the leukemia carries a FLT3, IDH or NPM1 change.
How Tambiciclib works
CDK9 is an enzyme that keeps the genes for short-lived survival proteins, including MCL-1, switched on. AML cells that stop responding to venetoclax often lean on MCL-1 instead of BCL-2. Blocking CDK9 lets MCL-1 levels fall within hours, which SELLAS reports pushes leukemia cells into apoptosis in laboratory studies, including cells with ASXL1 and TP53 mutations, and is meant to restore sensitivity to venetoclax[3].
Mechanism: Selective CDK9 inhibitor that shuts off short-lived survival proteins such as MCL-1 that let AML cells resist venetoclax
Side effects and safety
There is no FDA label. In the Phase 2 study of SLS009 with azacitidine and venetoclax in relapsed or refractory AML presented at ASH in December 2025, SELLAS reported no dose-limiting toxicities and no treatment-related deaths and described the combination as well tolerated; detailed adverse event rates have not been published in a label[3].
This is not a complete list of side effects. Talk to your doctor or pharmacist about what to expect and when to seek medical attention.
Taking Tambiciclib
Investigational, given by IV infusion in combination with venetoclax and azacitidine inside the Phase 1/2 study NCT04588922. It is available only through the trial[1].
Availability and cost
Only available as the brand-name product.
Clinical trial results
NCT04588922 is a Phase 1/2 study (160 patients planned, recruiting, primary completion December 30, 2026) that moved from single-agent dose escalation to combination cohorts with azacitidine and venetoclax[1].
At ASH 2025 SELLAS reported that among 35 evaluable patients with relapsed or refractory AML with myelodysplasia-related changes after earlier venetoclax, 46% responded (CR, CRi or MLFS) and 29% reached CR or CRi, with response rates of 48% in ASXL1-mutated and 57% in TP53-mutated disease and a median survival of 8.9 months in the least pretreated cohort[3].
The newly diagnosed expansion dosed its first patient in early 2026 and had enrolled 28 patients by August 11, 2026 out of a planned 80, including people expected to become refractory early to azacitidine and venetoclax; topline data are expected in the fourth quarter of 2026[2]. A European study of about 40 newly diagnosed patients through the IMPACT-AML STREAM network was announced in January 2026[3].
Development history
Tambiciclib was formerly known as GFH009 and is developed by SELLAS as SLS009. The FDA granted Rare Pediatric Disease Designation for pediatric ALL on June 24, 2024 and for pediatric AML on July 16, 2024, and the European Medicines Agency granted orphan designation for AML in July 2024[4][5]. SELLAS is also studying it in pancreatic cancer models.
Explore Acute Myeloid Leukemia trials
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Where to access Tambiciclib
Investigational: available only through clinical trial enrollment
Tambiciclib has not been approved by the FDA and is not available by prescription. The only way for a patient to receive Tambiciclib today is by enrolling in an active clinical trial and meeting that trial's eligibility criteria. Decisions about trial participation should be made with the specialist who manages the patient's condition and knows their current treatment.
Primary active trial
ClinicalTrials.gov record NCT04588922
View full trial record on ClinicalTrials.gov →Trial status, site list, and eligibility are pulled from ClinicalTrials.gov. Confirm current recruitment status and nearest site directly with the study team before traveling.
Common questions about Tambiciclib
▸What is Tambiciclib?
An investigational IV drug being tested with venetoclax and azacitidine, first in people whose AML came back after venetoclax and now in an 80-patient Phase 2 study of newly diagnosed AML, with topline results expected in the fourth quarter of 2026. It holds FDA Rare Pediatric Disease Designations for pediatric AML and pediatric ALL. It is not FDA approved.
▸How does Tambiciclib work?
CDK9 is an enzyme that keeps the genes for short-lived survival proteins, including MCL-1, switched on. AML cells that stop responding to venetoclax often lean on MCL-1 instead of BCL-2. Blocking CDK9 lets MCL-1 levels fall within hours, which SELLAS reports pushes leukemia cells into apoptosis in laboratory studies, including cells with ASXL1 and TP53 mutations, and is meant to restore sensitivity to venetoclax[3].
▸What are the side effects of Tambiciclib?
There is no FDA label. In the Phase 2 study of SLS009 with azacitidine and venetoclax in relapsed or refractory AML presented at ASH in December 2025, SELLAS reported no dose-limiting toxicities and no treatment-related deaths and described the combination as well tolerated; detailed adverse event rates have not been published in a label[3].
▸How is Tambiciclib taken?
Investigational, given by IV infusion in combination with venetoclax and azacitidine inside the Phase 1/2 study NCT04588922. It is available only through the trial[1].
▸Is Tambiciclib FDA approved?
Tambiciclib is currently in phase 2 clinical trials for Acute Myeloid Leukemia. It has not yet received FDA approval.
Sources and references
Every factual claim on this page is drawn from the public sources listed below. Click any reference to open the original document.
- ClinicalTrials.gov. Study of SLS009 (Formerly GFH009) a Potent Highly Selective CDK9 Inhibitor in Patients With Hematologic Malignancies. https://clinicaltrials.gov/study/NCT04588922
- SELLAS Life Sciences Group · 2026-08-11. SELLAS Life Sciences Reports Second Quarter 2026 Financial Results and Provides Corporate Update. https://ir.sellaslifesciences.com/news/News-Details/2026/SELLAS-Life-Sciences-Reports-Second-Quarter-2026-Financial-Results-and-Provides-Corporate-Update/default.aspx
- SELLAS Life Sciences Group · 2026-03-19. SELLAS Life Sciences Reports Full Year 2025 Financial Results and Provides Corporate Update. https://ir.sellaslifesciences.com/news/News-Details/2026/SELLAS-Life-Sciences-Reports-Full-Year-2025-Financial-Results-and-Provides-Corporate-Update/default.aspx
- SELLAS Life Sciences Group · 2024-06-24. SELLAS Announces U.S. FDA Rare Pediatric Disease Designation Granted to SLS009 for the Treatment of Pediatric Acute Lymphoblastic Leukemia. https://ir.sellaslifesciences.com/news/News-Details/2024/SELLAS-Announces-U.S.-FDA-Rare-Pediatric-Disease-Designation-Granted-to-SLS009-for-the-Treatment-of-Pediatric-Acute-Lymphoblastic-Leukemia/default.aspx
- SELLAS Life Sciences Group · 2024-07-16. SELLAS Announces U.S. FDA Rare Pediatric Disease Designation (RPDD) Granted to SLS009 for the Treatment of Pediatric Acute Myeloid Leukemia. https://ir.sellaslifesciences.com/news/News-Details/2024/SELLAS-Announces-U.S.-FDA-Rare-Pediatric-Disease-Designation-RPDD-Granted-to-SLS009-for-the-Treatment-of-Pediatric-Acute-Myeloid-Leukemia/default.aspx