Prospects for Sanofi’s dengue fever vaccine Dengvaxia look increasingly dim after it confirmed a long-debated safety issue with the product.
The company now has clinical data showing that there is a difference in the reaction to Dengvaxia depending on whether the recipient has had dengue fever in the past or not. In a nutshell, the vaccine works as expected in people already exposed to the virus, but in those who haven’t the vaccination is linked to an elevated risk of severe disease developing from a subsequent dengue infection.
Unlike most infectious diseases, dengue fever tends to be much more severe on a second infection, and the implication is that Dengvaxia is acting like a first ‘natural’ infection. That cuts down the eligible patient population for Dengvaxia by some margin, as it is less likely to be used in areas where the disease is less prevalent.
The first approval of Dengvaxia in Mexico in 2015 was hailed as a major turning point in the fight against dengue fever, and the fruition of more than two decades of R&D effort costing around $1.6bn. Dengue is the fastest spreading mosquito-borne viral disease and 40% of the world’s population lives under the threat of the virus, according to the World Health Organization (WHO).
The disease infects 390 million people a year and symptoms include fever, a hammering headache, flu-like symptoms, bone, muscle and joint pain, rash and nausea and vomiting. While most patients recover, the disease poses a considerable economic burden on society – it is estimated to cost India upwards of $500m a year for example – and causes around 20,000 deaths a year worldwide.
Despite its promise and €1bn-plus in sales projections it barely got out of the starting blocks before running into difficulties, which have been blamed on political disruption and economic problems in its first approved markets, and the Indian governments refusal to waive a requirement for local clinical trials of the vaccine.
Sales last year came in at €55m, well short of the €200m predicted by analysts – and has headed south in 2017, making just €22m in the first nine months of this year and €4m in the third quarter – a near 90% drop.
Commenting on the new analysis, Su-Peing Ng, global medical head for Sanofi’s vaccine division Sanofi Pasteur, said: “These findings highlight the complex nature of dengue infection. We are working with health authorities to ensure that prescribers, vaccinators and patients are fully informed of the new findings, with the goal of enhancing the impact of Dengvaxia in dengue-endemic countries.”
Sanofi is proposing that national regulatory agencies update the prescribing information for the vaccine to include a recommendation that healthcare professionals assess the likelihood of prior dengue infection in an individual before vaccinating.
The setbacks for Dengvaxia provide an opportunity for rival Takeda to leapfrog Sanofi with its own dengue vaccine candidate TAK-003, which has showed a higher rate of protective efficacy in phase II testing, and what appeared to be greater consistency in stimulating antibody responses against the four dengue virus serotypes. Industry watchers have suggested TAK-003 could be on the market by 2020.