Eli Lilly's drug tirzepatide has been granted "fast track" status by the Food and Drug Administration, which means it could win approval to be prescribed as an obesity treatment as early as late 2023. The drug, which was already approved in May as a treatment for Type 2 diabetes under the name Mounjaro, has the potential to be a blockbuster, analysts have said. Last month, UBS estimated peak annual sales will reach $25 billion , which would eclipse sales of AbbVie's rheumatoid arthritis treatment Humira, which currently holds the title of the "biggest drug ever." Lilly said Thursday that it plans to begin an application for FDA approval on a rolling basis by the end of this year, and will have results for its second phase-three clinical trial complete by the end of April. Wells Fargo analyst Mohit Bansal said it would typically take the FDA between six and 10 months to review the data, but the expedited process could shave time off the review, as data from its earlier clinical trials and manufacturing information can be submitted before the Surmount-2 trial is completed. "We see high likelihood of a 6-month review making approval in 4Q'23 likely," Bansal wrote in a research note. Morgan Stanley analyst Terence Flynn estimated a first-half 2024 launch of the product. Although this timing is in line with what the company had previously outlined, there had been some anticipation that the process could move even faster based on the strong results in the first of the two phase-three clinical trials. On par with bariatric surgery The company's Surmount-1 study had shown that patients lost between 16% and 22.5% of their body weight while taking the medication, which is much closer to the results achieved by bariatric surgery. More than 40% of U.S. adults have obesity, according to the Centers for Disease Control and Prevention , and its prevalence is expected to rise in the future. Obesity puts people at greater risk for a host of other conditions and costs the U.S. nearly $173 billion each year, in 2019 dollars, the CDC said. In July, Morgan Stanley had said it expected the weight loss market could be worth more than $50 billion by the end of the decade. Lilly shares were up slightly Thursday on the news, but the stock has gained more than 20% since the start of the year. On Sept. 28, it hit a 52-week high of $341.70. In a research note, Morgan Stanley's Flynn said any weakness in Lilly's stock is a buying opportunity. He rates the stock as overweight and has a price target of $412, which implies roughly 24% upside from Wednesday's close. More pressure on Novo Nordisk The timetable also turns up the heat for Novo Nordisk's competing treatment, Wegovy. Both drugs use glucagon-like peptide-1, or GLP-1, receptor agonists to slow gastric emptying, promote satiety and regulate blood sugar, but tirzepatide has a second incretin hormone, glucose-dependent insulinotropic polypeptide, or GIP. Wegovy has been shown to help patients lose about 15% of their body weight on average, and the drug has been very popular. However, sales have been constrained by manufacturing issues, which have limited its sales. In addition, the cost of the drug, which isn't always covered by health insurance plans, also prevents some patients from taking it. Wegovy has a list price of about $1,300 a month. Read more UBS upgrades Eli Lilly to buy, says it's developing possibly 'the biggest drug ever' Investors bet on obesity drugs before without much success. Why this next wave could be different Novo Nordisk shares were trading down less than 1% on Thursday. The company's stock is down nearly 6% year to date. Beyond its enormous potential as a treatment for diabetes, obesity and overweight, tirzepatide is also being studied as a treatment for a range of other conditions , such as kidney disease, sleep apnea, non-alcoholic steatohepatitis, pre-diabetes and cardiovascular issues. Bank of America's Geoff Meacham has estimated that the drug could reach as much as $100 billion in annual sales by 2035 if it were to win approval for these other illnesses. — CNBC's Michael Bloom contributed to this story.