A look at the best-selling drugs in 2017 shows the top spots dominated by monoclonal antibodies which, despite their age and looming competition, are still pulling in billions of dollars (Fig. 1a). The success of these huge franchises is partly down to the ability of manufacturers to continue to raise prices in the United States, even on these long-established assets, while years of industry lobbying has successfully delayed the impact of biosimilars in the world's biggest drugs market. AbbVie's Humira (adalimumab), with its standout US$18 billion of sales in 2017, is a prime example. Two biosimilar versions have been approved by the FDA, but a deal struck with Amgen means that the leading biosimilar, Amjevita, will not launch until 2023. However, having a cash cow in a portfolio can be both a blessing and a curse; Humira accounts for almost 70% of AbbVie's sales, so when it does eventually succumb to competition the impact will be huge for the company. Celgene, which marketed the second biggest-selling drug in 2017, is in a similar situation — Revlimid (lenalidomide) brought in 64% of the company's sales in 2017. Celgene's attempts at diversifying are proving to be less than successful, with the failure of mongersen in a phase III trial for Crohn's disease last year and the more recent regulatory set-back for multiple sclerosis therapy ozanimod, the company's biggest pipeline hope. Other products in the top ten could soon be falling down the ranking. Sales of Sanofi's Lantus are expected to slip substantially due to price erosion and the arrival of biosimilar insulins, while Pfizer's pain drug Lyrica (pregabalin) loses patent exclusivity in the United States at the end of this year.

Figure 1: Top drugs and companies by sales in 2017.
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a & Top ten drugs by sales globally, with monoclonal antibodies highlighted in purple . b & Top ten companies by sales of prescription and over-the-counter drugs. Source: EvaluatePharma.

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Sales of Lyrica, along with those of pneumococcal vaccine Prevnar 13 and breast cancer treatment Ibrance (palbociclib), helped Pfizer to become the biggest pharma company by total sales (including prescription drugs and over-the-counter drugs) in 2017 (Fig. 1b). Despite the loss of Lyrica sales due to generics, Pfizer is still expected to hang onto the top spot in 2018; should speculation of another mega-merger prove correct, the company's lead could widen further. Novartis, 2017's runner-up, is also set to hold onto its second place position in 2018, as sales of psoriasis drug Cosentyx (secukinumab) ramp up. Roche, however, is forecast to slip from third to fifth in the next 4 years as its dominant monoclonal antibody franchises — Rituxan (rituximab), Herceptin (trastuzumab) and Avastin (bevacizumab) — face biosimilar competition. These three products pulled in a combined $21 billion of sales in 2017, and despite high hopes for new launches such as the multiple sclerosis therapy Ocrevus (ocrelizumab), the immune checkpoint inhibitor Tecentriq (atezolizumab) in oncology and the haemophilia therapy Hemlibra (emicizumab), the decline of Roche's legacy giants will leave a big sales gap to plug. The extent of Roche's sales decline is nowhere near that forecast for Gilead Sciences, however, which is set to drop dramatically as its huge hepatitis C portfolio runs out of steam. Gilead's recent $12 billion purchase of one of the leaders in the chimeric antigen receptor (CAR) T therapy field, Kite Pharmaceuticals, was an effort to diversify into the hot area of immuno-oncology. Finally, Merck & Co. will be hoping that its growing presence in immuno-oncology, led by the immune checkpoint inhibitor Keytruda (pembrolizumab), will make up for declining diabetes sales; loss of market share in this therapy area contributed to the company's slip down the rankings from fifth to sixth place in 2017.