Cyclin D kinase 4/6 (CDK4/6) inhibitors have shown great improvement in extending progression-free survival (PFS) in patients with human epidermal growth factor-negative (HER2-) and hormonal receptor positive (HR+) metastatic breast cancer. Pfizer’s Ibrance (palbociclib) was the first CDK4/6 inhibitor to be approved in 2015, both in combination with an aromatase inhibitor and with Faslodex (fulvestrant) in the first- and second-line metastatic setting, respectively. Exploding onto the market, Ibrance has already reached blockbuster status, beating all other drugs to become the new standard of care and setting the bar high for new entrants.

Hoping to get a piece of the pie, two other inhibitors, Novartis’ ribociclib and Eli Lilly’s abemaciclib, are expected to be approved by the end of 2017 in the same disease. GlobalData expects to see fierce competition in 2017 between the three pharma giants in this lucrative patient segment, wherein their individual development strategies will set them apart from each other.

Ibrance and ribociclib are poised to dominate this drug class in terms of sales. Ibrance has the coveted first-to-market advantage, but Novartis hopes its combinatory strategy for ribociclib will lead to best-in-class status, setting it apart from the competition. Following impressive data presented late in 2016, Novartis was able to stop ribociclib’s registration trial early and file for approval, making up for lost ground. The time lag between the launch of Ibrance and ribociclib is set to be less than a year in the EU, much smaller than the two-year period observed in US, narrowing Ibrance’s advantage. Ribociclib could be rapidly adopted by patients who are able to enter early access schemes in certain European countries.

GlobalData believes that, despite Novartis’ best efforts, it will not beat Ibrance in terms of sales by 2023

GlobalData believes that, despite Novartis’ best efforts, it will not beat Ibrance in terms of sales by 2023. However, the companies’ ability to win over stakeholders will determine how big the difference will be between both products. Lagging far behind, abemaciclib has failed to meet the pre-planned interim analysis of its pivotal trial, and has shown potentially limiting gastro-intestinal toxicities. While opportunities remain for Eli Lilly to leverage the monotherapy activity of abemaciclib, particularly in latter lines of therapy and in endocrine-resistant patients, GlobalData thinks it may be too little too late.

Like Novartis, Eli Lilly designed a trial that could be stopped early if the data looked promising, which would help it close the gap on its competitors. However, on August 10, 2016, the company announced that the trial did not meet the criteria set to terminate the trial early. The launch of abemaciclib is set to come almost three years after the launch of Ibrance in the US, presenting Eli Lilly with an uphill battle to gain market share.

While Pfizer will likely be the stand-out winner, with a long awaited mega-blockbuster in breast cancer to add to their oncology portfolio, all of the inhibitors are going to be widely adopted by physicians across the major markets. GlobalData forecasts sales of $4.8 billion by 2023 in the US, Spain, UK, Italy, Germany, France, Japan, and China, corresponding to almost half of the HER2-/HR+ breast cancer market size.