Almost everyone will eventually have drug resistance
For the tens of thousands of Americans each year who face acute myeloid leukemia, the disease's cruelest feature has never been its initial ferocity but its patience — the way it waits, adapts, and outlasts the medicines meant to stop it. Researchers at Oregon Health & Science University have now identified a pairing of two existing drugs, venetoclax and palbociclib, that appears to close the biological door through which leukemia cells have long escaped. Tested across more than 300 patient samples and confirmed in animal models, the combination interrupts the cellular machinery that tumors use to survive standard treatment, offering a potential path forward where, until now, resistance has been nearly inevitable.
- Nearly every AML patient treated with the current standard therapy eventually develops resistance, leaving a disease with a five-year survival rate of only 25–40% with almost no reliable second act.
- Researchers tested 25 drug combinations and found that adding palbociclib — a breast cancer drug — to venetoclax outperformed all others, blocking the protein-production surge that leukemia cells use to survive venetoclax alone.
- In mouse models carrying human leukemia cells with known resistance mutations, venetoclax alone extended no survival at all, while the combination kept most animals alive for nearly a year — one outlasting the study itself.
- A genome-wide CRISPR screen revealed the two drugs attack different survival pathways simultaneously, suggesting the combination could address most known resistance mechanisms rather than simply delaying the same problem.
- The research team is already evaluating related drugs and preparing to move toward clinical trials, with lead researcher Melissa Stewart — herself a breast cancer survivor — describing the work as both scientific and deeply personal.
Researchers at Oregon Health & Science University have identified a drug combination that may finally give acute myeloid leukemia patients a way past one of cancer medicine's most persistent walls: the ability of tumors to learn, adapt, and survive the treatments designed to kill them.
AML strikes more than 20,000 Americans each year and remains brutally efficient. Since 2019, doctors have relied on venetoclax paired with azacitidine as a frontline approach — an improvement in early response, but not a solution. Almost every patient eventually develops resistance, and the five-year survival rate has remained stubbornly fixed between 25 and 40 percent.
The new study, published in Cell Reports Medicine, tested 25 drug combinations against more than 300 patient samples. The pairing of venetoclax with palbociclib — already approved for breast cancer — emerged as the clear leader. Lead researcher Melissa Stewart's team found the biological reason: when leukemia cells encounter venetoclax alone, they survive by accelerating protein production. Palbociclib shuts down that escape by regulating the cellular machinery behind it. Patient samples that responded most strongly showed a measurable silencing of protein-synthesis genes.
The finding held in mouse models carrying human leukemia cells with mutations known to cause resistance. Venetoclax alone did nothing to extend survival in these animals. The combination kept most of them alive for 11 to 12 months — one was still living when the study concluded. A genome-wide CRISPR screen added further weight: the two drugs appear to work through distinct pathways, closing multiple survival routes at once rather than simply delaying the same failure.
Corresponding author Jeffrey Tyner, a co-leader of the national Beat AML program, noted that the discovery required following the data across traditional cancer boundaries — a breast cancer drug illuminating a leukemia solution. Stewart, who is herself a breast cancer survivor treated at OHSU, described the work as carrying personal as well as scientific meaning. The team is already evaluating related drugs and sees a clear path toward clinical trials, with Tyner predicting the combination could address most known resistance mechanisms to current standard therapy.
Researchers at Oregon Health & Science University have identified a drug pairing that may help acute myeloid leukemia patients escape one of the most stubborn problems in cancer treatment: the way tumors learn to survive standard therapy. The finding, published in Cell Reports Medicine, emerged from testing more than 300 patient samples and animal models, and it points toward a clinical path that could reshape how doctors approach a disease that kills with brutal efficiency.
Acute myeloid leukemia strikes more than 20,000 Americans each year, making it one of the most common forms of leukemia and among the most aggressive. For nearly six years, since the FDA approved venetoclax in 2019, doctors have paired it with azacitidine as a frontline treatment. The combination improved how patients responded initially and how they felt. But it could not solve the core problem: almost every patient eventually develops resistance. The five-year survival rate remains stuck between 25 and 40 percent.
The new study tested 25 different drug combinations against AML samples and found that pairing venetoclax with palbociclib—a drug already approved for breast cancer—produced significantly stronger and more durable results than venetoclax alone. Melissa Stewart, the lead researcher, and her team discovered why the combination works. When leukemia cells are exposed to venetoclax by itself, they adapt by ramping up protein production, a shift that allows them to survive. Palbociclib blocks this escape route by regulating the cellular machinery that makes those proteins. Patient samples that responded most strongly to the combination showed a clear shutdown of genes involved in protein synthesis.
The researchers confirmed the finding in mouse models carrying human leukemia cells with mutations known to cause venetoclax resistance. Venetoclax alone did nothing to extend survival in these animals, which matched what the genetics predicted. But when combined with palbociclib, most of the mice lived 11 to 12 months. One mouse was still alive when the study ended. A genome-wide CRISPR screen revealed something else important: the combination therapy does not rely on the same cellular vulnerabilities that make venetoclax alone more effective when certain protein-production genes are lost. The two drugs appear to work together, shutting down multiple survival pathways at once.
Jeffrey Tyner, the study's corresponding author and a co-leader of the national Beat AML program, emphasized that the finding emerged from following data wherever it led, even across traditional cancer boundaries. Some might question why a breast cancer drug would help with leukemia, but biology does not respect those lines. Stewart, who is herself a breast cancer survivor treated at OHSU, said the work holds personal weight. "The hope that research and clinical trials can bring—that's what motivates me," she said. The team is already evaluating other drugs similar to palbociclib, many also approved for breast cancer, to expand future trial options.
Neither researcher has tested the combination in patients yet. But based on the laboratory evidence, Tyner predicted that the pairing would mitigate most known resistance mechanisms to current standard therapy. Moving from the lab to the clinic will require work—regulatory approval, trial design, patient recruitment. But the researchers see the path clearly now. This is the kind of finding that justifies the long hours in the lab: a concrete possibility where, before, there was only the grim certainty of resistance.
Notable Quotes
Almost everyone will eventually have drug resistance to current AML therapy— Jeffrey Tyner, OHSU
This combination would mitigate most known resistance mechanisms to current standard therapy— Jeffrey Tyner, OHSU
The Hearth Conversation Another angle on the story
Why does a breast cancer drug work against leukemia? That seems like a strange connection.
It's not strange once you understand the mechanism. Palbociclib regulates how cells make proteins. That survival pathway exists in both cancers. The researchers weren't looking for a breast cancer drug specifically—they tested 25 combinations and this one won. It just happened to be approved for something else.
But almost everyone develops resistance anyway. What makes you think this combination will be different?
Because it works on multiple fronts at once. Venetoclax alone, the leukemia cells adapt by making more protein. Palbociclib stops that adaptation. The CRISPR data showed the combination doesn't rely on a single vulnerability the way venetoclax alone does. It's harder for cells to escape two mechanisms simultaneously.
How close are we to actual patients taking this?
Still in the preclinical stage. They've tested it in lab samples and mice. The next step is designing a clinical trial and getting regulatory approval. That takes time. But the researchers are already looking at similar drugs to expand options.
What does 25 to 40 percent five-year survival really mean for someone diagnosed with AML?
It means the disease is still largely fatal. Even with the best current treatment, most people don't make it five years. That's why resistance is so devastating—it's not just a setback, it's often the end of options. A combination that could prevent or delay resistance changes that calculus entirely.