Japan approves Mounjaro for type 2 diabetes

Japan's Ministry of Health, Labour and Welfare approved Mounjaro (tirzepatide) for type 2 diabetes on September 26, 2022, according to a joint announcement from Eli Lilly Japan and Mitsubishi Tanabe Pharma Corporation ^[1]. The companies describe it as the world's first sustained-release drug that activates both the GIP and GLP-1 receptors, delivered once weekly by subcutaneous injection using a single-use autoinjector called ATEOS ^[1].

The Japanese approval covers six dose strengths, from 2.5 mg up to 15 mg, with a standard maintenance dose of 5 mg weekly after a four-week starting period at 2.5 mg ^[1]. Doses can be raised in 2.5 mg steps at intervals of four weeks or longer, up to the 15 mg maximum, based on how a patient responds ^[1].

The decision rested on results from four phase 3 trials ^[1]. Two were conducted in Japan: SURPASS J-mono, which enrolled 636 adults and found that tirzepatide at 5 mg, 10 mg, and 15 mg reduced HbA1c more than dulaglutide 0.75 mg after 52 weeks, the study's main goal ^[1]. SURPASS J-combo enrolled 443 adults already on one oral diabetes drug and tracked adverse events over 52 weeks while also measuring blood sugar improvements ^[1]. Two global trials also factored into the review. SURPASS-1, with 478 participants including 89 from Japan, showed tirzepatide beat placebo on HbA1c reduction after 40 weeks in patients not yet on injectable therapy ^[1]. SURPASS-5, with 475 participants including 82 from Japan, tested tirzepatide added to insulin glargine, also over 40 weeks ^[1].

Japan's clearance came after the drug's approval in the United States on May 13, 2022, where Eli Lilly launched it on June 7, and after European Union approval on September 15, 2022 ^[1]. In Japan, Mitsubishi Tanabe Pharma will handle distribution and sales, while both companies share information duties under a sales agreement signed in July 2022 ^[1].

Why it matters for patients

This approval expanded the countries where tirzepatide is available under the brand name Mounjaro for type 2 diabetes, following its earlier US and EU clearances the same year ^[1]. For patients in the United States, the news itself does not change access or price, since Mounjaro was already approved domestically months earlier ^[1]. But the Japanese trial data adds to the broader evidence base for tirzepatide, showing it outperformed an existing GLP-1 drug, dulaglutide, on blood sugar control in a Japanese population over one year ^[1].

The press release also notes that tirzepatide was, at the time, still in phase 3 development for additional uses beyond diabetes, including chronic weight management and heart failure with preserved ejection fraction, as well as being studied for a liver condition called NASH ^[1]. Tirzepatide later became available in the US under the brand name Zepbound for weight management, though that approval is not detailed in this source and came after this announcement.

Any questions about how dosing, side effects, or eligibility apply to a specific patient are not addressed in this release, which focuses on the regulatory decision and trial design rather than individual treatment guidance ^[1].

What happens next

The sources do not describe a specific Japanese launch date for Mounjaro following the September 26, 2022 approval, nor do they detail post-approval monitoring plans ^[1]. Broader developments in tirzepatide's use for weight management and other conditions were still in phase 3 testing as of this announcement, according to the companies ^[1].