Dive Brief:
- Pfizer on Tuesday said a key experimental medicine helped stave off disease progression in a Phase 2 trial of patients with metastatic breast cancer.
- Atirmociclib is designed as a next-generation improvement on Pfizer’s Ibrance, the pioneer in a class known as cyclin-dependent kinase, or CDK 4/6 inhibitors. The drugs, which block proteins that tumors use to grow and multiply, have become a pillar of care for a common type of breast cancer known as HR+/HER2-.
- The new study, dubbed Fourlight-1, tested atirmociclib in patients who had previously tried CDK4/6 inhibitors. Researchers found that those given the experimental drug in combination with a widely used hormone therapy called fulvestrant had a 40% reduction in the risk of disease progression or death compared with those on another combination of medicines.
Dive Insight:
Pfizer’s Ibrance long dominated the $15 billion market for CDK4/6 inhibitors. But in recent years it’s been losing ground to Eli Lilly’s Verzenio and Novartis’s Kisqali, which have won new patients with research that highlighted treatment advantages of their medicines. Pfizer, meanwhile, failed in a bid to expand Ibrance’s use to patients with early disease.
Atirmociclib aims to improve on the class by focusing on CDK4 alone, potentially offering the possibility of better efficacy and tolerability for patients. Roche and BeOne Medicines, formerly BeiGene, are trying similar approaches.
On Tuesday, Pfizer Chief Oncology Officer Jeff Legos said he was especially encouraged by the fact that atirmociclib helped patients whose disease progressed soon after trying CDK4/6 inhibitors, a group that is historically difficult to treat.
“The strength of these data reinforces our confidence that atirmociclib may meaningfully differentiate from the CDK4/6 inhibitor class,” Legos said in Pfizer’s statement. “We are continuing to accelerate development of this next-generation cell cycle inhibitor in earlier lines of therapy where it may offer even greater benefit for patients.”
Pfizer had originally designed Fourlight-1 as a Phase 3 study and then downgraded the trial as it shifted the focus for the drug to first-line treatment and patients with earlier disease. A Phase 3 study looking at atirmociclib as a first-line therapy for metastatic disease is already under way.
The new drug “is a critical piece” of Pfizer’s strategy to build its oncology business, RBC Capital Markets analyst Trung Huynh wrote in a note to clients. He estimates peak sales of $2.6 billion for the medicine, with an expected launch in 2027.
