FirstWord Lists – The best selling drugs in 2014

It is no wonder that biosimilar bulls are emerging. The 10 biggest selling pharmaceutical products in 2014 generated combined sales of $83 billion, of which $60 billion was generated by seven biologic drugs, most of which will lose exclusivity for key patents by the end of the decade.

The 'value' of this commercial opportunity has long been touted by biosimilar developers and, of course, only represents one part of the equation. Both the development and regulatory environments continue to provide a multitude of challenges, while convincing physicians and patients to use biosimilars at the expense of heavily entrenched brands is likely to prove the most difficult challenge of all – the flip side to the potential 'demise' of these products is their impressive longevity in the market.

However, an intensification of the debate around pricing in the US drug market and concerted regulatory momentum from the FDA in the past few months will frame this list of best-selling medicines in a slightly different light to previous years, when the prospect of significant biosimilar erosion appeared just that little bit less tenable.

In a note to investors published last week, Citi analysts led by Andrew Baum have taken the most bullish stance yet on the biosimilars opportunity; one headline grabbing conclusion from Citi's research is that sales of AbbVie's anti-TNF therapy Humira will decline from a peak of $16 billion in 2017 to $6 billion by 2022.

The rest of the analyst community are yet to reach the same conclusion; consensus forecasts sourced from Bloomberg indicate healthy sales of $14.8 billion for Humira in 2020, while it should be noted that Citi's outlook is not all doom and gloom; cost savings sourced from the use of biosimilars will be used to fund uptake of novel therapies, with Baum among the most bullish about the immuno-oncology market among his peers.

The Citi outlook is partly based on the notion of US pharmacy benefit managers – empowered by their success in the hepatitis C market – targeting the anti-TNF class for rapid adoption of biosimilars. It is Celltrion's biosimilar version of the anti-TNF Remicade – which is to be assessed by an FDA AdCom panel next month – that may provide the first opportunity for Citi's scenario to play out.

Consensus forecasts suggesting that Remicade sales will decline to around $7.6 billion by 2020 illustrate the Johnson & Johnson and Merck & Co.-marketed product as being the most exposed to direct biosimilar competition. Not only could Celltrion's product feasibly be approved by the FDA later this year, but is already cleared in Europe and on the verge of launching in some of the region's largest markets (Physician Views Poll Results: Let the games begin – Remicade biosimilar free to debut in EU5 markets).

Sanofi's basal insulin product Lantus is also set to face biosimilar competition (from Eli Lilly) in Europe this year, although a forecast decline in sales over the next five years primarily reflects a more challenging US price environment, loss of share to competitors and the switching of patients to Sanofi's Toujeo franchise, which is expected to gain FDA approval later this year.

Mirroring Sanofi's Toujeo strategy it is not surprising that 'successor' products to three other drugs on the list have launched in the past few years. Roche has sought to reduce its top line to exposure from biosimilar competition by launching Gazyva as a mooted successor to Rituxan with Perjeta and Kadcyla positioned as follow-ons to Herceptin (with this strategy a mixed success following publication of the MARIANNE data in December).

GlaxoSmithKline has sought to maintain leadership of the asthma and COPD markets via the launches of Breo Ellipta and Anoro Ellipta. While Advair has lost share over the past year in the US due to pricing dynamics, however, both Breo and Anoro have underwhelmed since launch. As a result, emphasis is building on a triple combination therapy in Phase III development but Advair looks well set to remain the biggest selling respiratory drug of all time. A key point of debate is whether Advair will face generic competition in the US next year; consensus suggests not, but this is a potential 'black swan' event in waiting for the UK player.

The final word must go to Gilead Sciences' Sovaldi hepatitis C franchise, which generated sales of $10.3 billion in 2014, a staggering performance following first launch in December 2013. Factoring in sales of Harvoni (a combination of Sovaldi with ledipasvir), franchise revenues swell to $12.4 million (Harvoni only launched in December 2014).

Sovaldi/Harvoni has not only emerged as the fastest drug launch of all time, but a controversial product that has stirred much of the current debate around US drug pricing. Whether the franchise can overtake Humira and Pfizer's Lipitor as the biggest selling remains to be seen, but consensus indicates 2020 sales of around $16 billion.

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