LONDON/COPENHAGEN, Aug 6 (Reuters) – Danish drugmaker Novo Nordisk (NOVOb.CO), opens new tab is facing a major challenge to its blockbuster weight-loss drug Wegovy.Booming sales of Wegovy powered the company to become Europe’s most valuable, but it has lost over $400 billion in market capitalization since mid last year as competition from U.S. rival Eli Lilly and Co (LLY.N), opens new tab and copycat rivals has hardened.Keep up with the latest medical breakthroughs and healthcare trends with the Reuters Health Rounds newsletter. Sign up here.The firm, whichh reports second-quarter results on Wednesday, has appointed a new CEO, veteran insider Maziar Mike Doustdar, who will take the reins on Thursday, and now needs to win over investors skeptical he can turn the firm’s fortunes around. Market Talk: Will the Bank of England accelerate its easing pace?Here are some of the challenges facing the firm as it looks to bolster sales and fend off challengers after a profit warning last week sparked a share price rout.WEGOVY VS ZEPBOUNDNovo has seen Eli Lilly’s rival drug Zepbound overtake it in terms of prescriptions in the key U.S. market this year. With Wegovy, Novo was first-to-market with a highly effective obesity treatment, which was approved in the U.S. in 2021. Lilly launched Zepbound in late 2023.Advertisement · Scroll to continueAd ChoicesSponsored Content3 Trends Shaping Financial Sector Investing3 Trends Shaping Financial Sector InvestingBy Morgan StanleyNovo’s Wegovy vs Eli Lilly’s Zepbound: U.S. prescriptionsNovo’s Wegovy vs Eli Lilly’s Zepbound: U.S. prescriptionsLOSING GROUNDNovo has seen its share price fall steeply versus rivals over the last year.A line chart showing that Novo Nordisk stock versus its rivals over the past year.A line chart showing that Novo Nordisk stock versus its rivals over the past year.VALUE PREMIUM SLIPPINGThat has brought its price-earnings ratio back in line with peers. It had previously commanded a wide premium.RISING COSTSThe drugmaker has seen costs rise as it has spent billions to expand manufacturing and sales capacity.NO LONGER TOP DOGNovo, valued at $650 billion in June last year, has shed over two-thirds of its value since. Its latest market cap is around $212 billion.Reporting by the future of awareness