Daiichi Sankyo was in the unusual position of having two drugs up against an FDA advisory committee yesterday, but only managed to get a positive vote in favour of one of them.
The panel voted by eight to three against the motion that quizartinib’s benefits outweighed its risk as a treatment for relapsed or refractory FLT3-positive acute myeloid leukaemia (AML), but separately gave Daiichi Sankyo some succour by backing pexidartinib for a rare condition called tenosynovial giant cell tumour (TGCT).
The verdict for FLT3 inhibitor quizartinib is the bigger deal for the company unfortunately, as the rejection looks set to put the drug even further behind Astellas’ rival drug for FLT3-positive relapsed AML – Xospata (gilteritinib) – which picked up an FDA approval in this setting last November and was launched in Japan last December.
Xospata is starting to bring in its first revenues – adding 2.5bn yen ($22m) to Astellas’ top-line before the end of April, and the company is predicting revenues will reach more than 15bn yen ($137m) in the coming fiscal year.
Approximately 25-30% of patients with AML have a mutation in the FLT3 gene which causes a particularly aggressive form of the disease with a higher risk of relapse.
Quizartinib’s failure to clear the panel wasn’t a complete surprise, as a briefing document published by the FDA reviewer ahead of the committee meeting revealed the agency had misgivings about the design of the study, particularly an “imbalance in early censoring and patients randomised but not treated between the arms” which could have resulted in a bias.
The FDA had previously extended its review time for quizartinib by three months as it digested the results, which found a 1.5-month improvement in overall survival for quizartinib compared to chemotherapy. The reviewer was also worried about the reliability of the data given inconsistencies in results between subgroups in the study.
Antoine Yver
“While we are disappointed by the outcome of today’s…vote, we will work closely with the FDA as it completes the review of our submission,” said Antoine Yver, Daiichi Sankyo’s global head of oncology R&D.
Novartis’ Rydapt (midostaurin) was the first FLT3 inhibitor to reach the market in 2017, and is used alongside chemotherapy for newly-diagnoses FLT3-positive AML. Both quizartinib and gilteritinib are aimed at second-line therapy.
Daiichi Sankyo acquired quizartinib as part of its $410m takeover of Ambit Biosciences in 2014, and has said it expected the drug to be its first entry in the oncology category.
The company has been working towards building a cancer business for several years through in-house R&D and a series of cancer alliances, and has indicated that it hopes to bring in 500bn yen in annual sales from the business in fiscal 2025.
The pexidartinib recommendation in TGCT is welcome of course, and sets up an FDA verdict in August. If approved it will be the first systemic drug that can offer an alternative to surgery for this form of benign tumour, which can cause damage to the joints and surrounding tissues.
Daiichi Sankyo acquired the drug when it bought Taiwanese firm Plexxikon for almost $1bn in 2011. TGCT affects fewer than two in a million people in the US, but the greater potential for pexidartinib – which inhibits colony stimulating factor-1 receptor (CSF1R) – is in follow-up indications such as stomach cancer.
The Japanese company has plenty of other candidates in its emerging oncology pipeline, including HER2-targeting antibody-drug conjugate DS-8201 (trastuzumab deruxtecan), a rival to Roche’s Kadcyla in breast cancer, which was licensed in a deal worth up to $6.9bn by AstraZeneca in March.