A New Hope for High-Risk AML: AB Science's AB8939 Shines in Early Trial

PARIS, FRANCE – June 29, 2026 – In the relentless battle against acute myeloid leukemia (AML), the deadliest form of leukemia in adults, glimmers of hope often emerge from the earliest stages of clinical research. Today, French pharmaceutical company AB Science provided one such glimmer, reporting compelling preliminary results from a Phase 1 study of its drug candidate, AB8939. For a small group of patients with highly aggressive, treatment-resistant AML, a new combination therapy has demonstrated remarkable efficacy, achieving a 67% overall response rate where standard options frequently fail.

While the data comes from just six individuals, the context is critical: these were not average patients. They were heavily pre-treated, battling second-, third-, or even fourth-line relapsed or refractory AML, and burdened with adverse genetic profiles that render the disease notoriously difficult to treat. The findings, though early, suggest a potent new strategy may be on the horizon for those with the bleakest prognoses.

A Striking Response in the Toughest Cases

The Phase 1 trial evaluated AB8939 in combination with venetoclax, a now-standard AML therapy. The results from this cohort are striking. Of the six patients treated, four showed a significant reduction in their cancer, and the other two saw their disease stabilize, culminating in a 100% disease control rate. This was achieved after just one 14-day treatment cycle, a rapid response in a setting where time is precious.

To appreciate the significance of a 67% response rate, one must understand the landscape. For this specific population—patients with adverse-risk genetics who have failed multiple prior treatments—existing therapies typically yield response rates between 10% and 30%. Median survival can be less than a year. The AB Science trial included patients with some of the most challenging genetic markers, including TP53 mutations, complex karyotypes, and MECOM-rearrangements, all associated with aggressive disease and poor outcomes.

Perhaps most notably, two of the responding patients had previously progressed on therapies that included venetoclax, the very drug used in this new combination. This suggests AB8939 may not just complement venetoclax but could potentially re-sensitize or overcome resistance to it. Furthermore, the combination was well-tolerated, with no dose-limiting toxicities observed, allowing researchers to confidently select a dose for larger, more definitive studies.

"This new data is very encouraging, particularly considering the very adverse risk profile of this patient’s leukemia," said Nicholas J. Short, MD, an Associate Professor at MD Anderson Cancer Center. "These early efficacy and safety data suggest that AB8939 can be combined with venetoclax and could have significant activity in the highest-risk subtypes of AML."

The Science of Overcoming Resistance

The promising clinical results are rooted in AB8939's unique, dual-pronged mechanism of action, which appears purpose-built to tackle the core challenges of AML: drug resistance and relapse. The drug functions as both a microtubule destabilizer and an inhibitor of cancer stem cells.

First, it disrupts microtubules, the internal scaffolding essential for cell division. This action, which induces programmed cell death (apoptosis), is highly potent in rapidly dividing leukemia cells. Crucially, AB8939 seems to evade the common resistance mechanisms that plague older microtubule-targeting drugs. It is not ejected from cancer cells by multi-drug resistance pumps and is not degraded by enzymes within the bone marrow, allowing it to maintain its effectiveness.

Second, and perhaps more critically for long-term success, AB8939 targets the source of relapse: leukemia stem cells (LSCs). These cells, which can lie dormant and resist conventional chemotherapy, are the seeds from which the cancer regrows. AB8939 inhibits ALDH, an enzyme family crucial for the survival of these LSCs. By eliminating the stem cells, the drug holds the potential not just to shrink tumors, but to prevent them from returning.

This dual action creates a powerful synergy with venetoclax. Venetoclax works by inhibiting BCL-2, a protein that cancer cells use to evade apoptosis. By blocking this survival signal, venetoclax primes the cells for death. AB8939 then delivers the decisive blow by disrupting cell division, while simultaneously wiping out the reservoir of cancer stem cells that venetoclax may not effectively target. This combined assault may explain its efficacy even in patients whose cancers had learned to resist venetoclax alone.

Charting the Path from Lab to Market

Positive early data is a crucial first step, but the journey to regulatory approval and patient access is long and expensive. AB Science appears to be building a strategic framework to support AB8939's development. The company estimates the addressable market for relapsed or refractory AML exceeds €2 billion annually, a substantial incentive for further investment.

To protect this potential, the company has secured a robust intellectual property position, with patents that could extend protection into the 2040s for specific AML subpopulations. It has also obtained Orphan Drug Designation from both the U.S. FDA and the European Medicines Agency (EMA). This status provides significant benefits, including development incentives and a period of market exclusivity—seven years in the U.S. and ten in Europe—following approval, which is a critical advantage for a smaller biotech firm.

As an R&D-focused company, AB Science relies on external funding to advance its pipeline. The firm's strategy hinges on generating data compelling enough to secure a major partnership. The next steps are designed to do just that. The company plans to initiate Step 4 of the trial, evaluating a triple combination of AB8939, venetoclax, and azacitidine (another standard AML therapy). It will also launch an expansion study of the two-drug combination in about 15 patients to generate more robust evidence. These upcoming results will be a critical test, providing the clearer picture needed to confirm AB8939's role in changing the future for patients with high-risk AML.