Trial sets up showdown between Ibrance and Novartis' ribociclib

Novartis has halted a phase III trial of its CDK 4/6 inhibitor ribociclib early after the drug met its objectives, putting an early approval for the drug on the table.

An interim look at the data showed ribociclib achieved the goal of a significant increase in progression-free survival (PFS) in breast cancer, and Novartis now says it will start talking to regulators about regulatory filings.

Approval would make ribociclib the first direct competitor to Pfizer's first-in-class CDK 4/6 inhibitor Ibrance (palbociclib), which has been growing at a phenomenal pace since its approval last year and achieved first-quarter 2016 sales of $429m.

The results of the MONALEESA-2 trial showed that ribociclib (LEE011) given in combination with Novartis' hormone therapy Femara (letrozole) extended PFS compared to letrozole alone in postmenopausal women with previously-untreated hormone receptor positive (HR+), HER-2 negative advanced breast cancer.

While PFS data may support approval Novartis is continuing to follow-up patients in the study to see if its drug also has an impact on overall survival.

Ibrance is approved alongside Femara for the same patient population, so ribociclib will compete head-to-head in the market if regulators approve the drug, with another candidate (abemaciclib) from Eli Lilly also in late-stage testing.

Novartis' chief medical officer Vasant Narasimhan said recently that the company expects ribociclib to "capture a significant portion in a three-player market".

The company also indicated that it will be evaluating expanded access programmes in some regions to help ensure women who may benefit from ribociclib have access to the drug.

If approved, ribociclib will slot into Novartis' portfolio alongside Femara and also mTOR inhibitor Afinitor/Votubia (everolimus), which is also approved for HR+/HER2- breast cancer amongst other indications and brought in $1.6bn in sales last year.

The arrival of Ibrance on the market has pegged back Afinitor's growth and pushed it to later-line use, although the company believes many breast cancer patients will still end up receiving the drug.

Novartis is also testing ribociclib in combination with AstraZeneca's hormonal therapy Faslodex (fulvestrant) in the MONALEESA-3 study - due to generate results in 2018 - and is looking into possible combinations with its PI3 kinase delta inhibitors BYL719 and buparlisib (BKM120).