Japan approves Zepbound for obesity disease

Eli Lilly Japan and Mitsubishi Tanabe Pharma Corporation said on December 27, 2024 that Japan's Ministry of Health, Labour and Welfare approved Zepbound (tirzepatide) for the chronic disease of "obesity disease" with multiple factors ^[1]. It is the same molecule already sold in Japan as Mounjaro for type 2 diabetes, launched there in April 2023 ^[1].

The Japanese indication is unusually specific. Use is limited to people who have hypertension, dyslipidemia, or type 2 diabetes, who have not responded adequately to diet or exercise therapy, and who also meet one of two thresholds: a BMI of at least 27 kg/m² along with at least two obesity-related health conditions, or a BMI of at least 35 kg/m² ^[1]. That is a tighter gate than the general framing of the US obesity approval, though the companies' announcement does not spell out the US eligibility criteria for comparison; it only notes that tirzepatide has been sold in the United States as Zepbound for obesity since December 2023 ^[1].

What the approval is based on

The approval rests mainly on SURMOUNT-J (NCT04844918), a Phase 3, multi-center, randomized, double-blind, placebo-controlled trial in Japanese adults ^[1]. At week 72, average body weight fell 17.8% in the tirzepatide 10 mg group (n = 71) and 22.7% in the 15 mg group (n = 76), compared with 1.7% in the placebo group (n = 75) ^[1]. Both doses were superior to placebo ^[1].

On the responder measures, 94.4% of people on 10 mg and 96.1% on 15 mg lost at least 5% of body weight, versus 20.0% on placebo ^[1]. Secondary endpoints looking at 7%, 10%, 15% and 20% weight loss at week 72 also favored both tirzepatide doses over placebo ^[1].

Everyone in the trial received counseling on diet and exercise from national registered dietitians or equivalently qualified staff, under low-calorie diet and exercise therapy described in Japan's obesity management guidelines ^[1]. People with diabetes were excluded, as were those who had recently used weight-loss drugs or undergone device-based obesity treatment ^[1].

How Japan defines obesity

Japan uses different BMI cutoffs than the United States. There, "obesity" starts at a BMI of 25 kg/m², and a BMI of 35 or above is called "high-degree obesity" ^[1]. "Obesity disease" is a separate diagnosis: obesity plus at least one obesity-induced or obesity-associated disorder, or visceral fat accumulation, that medically requires weight reduction ^[1].

The list of qualifying disorders includes glucose intolerance, dyslipidemia, hypertension, hyperuricemia or gout, coronary artery disease, cerebral infarction or transient ischemic attack, non-alcoholic fatty liver disease, menstrual disorder or female infertility, obstructive sleep apnea or obesity hypoventilation syndrome, musculoskeletal disorders, and obesity-related kidney disease ^[1]. Roughly 28 million people in Japan are estimated to be living with obesity, based on the 2022 National Health and Nutrition Survey ^[1].

The approved Japanese dosing mirrors Mounjaro's: six dose strengths of 2.5 mg, 5 mg, 7.5 mg, 10 mg, 12.5 mg and 15 mg, given once weekly by subcutaneous injection with the single-use ATEOS autoinjector ^[1]. The label describes starting at 2.5 mg weekly, increasing by 2.5 mg every four weeks to 10 mg, with the option to reduce to 5 mg or go up to a maximum of 15 mg depending on the patient ^[1].

Why it matters for patients

For US readers, this approval does not change anything about how Zepbound is prescribed or covered in the United States. It is a separate national decision with its own eligibility rules ^[1].

What it does show is how differently regulators can draw the line around the same drug. Japan's label requires a named condition — hypertension, dyslipidemia, or type 2 diabetes — plus either a BMI of 35 or a BMI of 27 with two obesity-related conditions ^[1]. That framing treats the medicine as a treatment for a defined disease with complications, not for elevated BMI alone.

The Japanese trial results are also a useful data point because they come from a Japanese population with a 72-week endpoint ^[1]. The companies did not publish safety details, pricing, reimbursement terms, or a launch date in this announcement, so those remain unknown ^[1]. Mitsubishi Tanabe is responsible for sales and distribution in Japan, with both companies jointly providing information, as they do for Mounjaro ^[1].

What happens next

Marketing authorization was granted December 27, 2024 ^[1]. A launch date and supply plans were not disclosed in the announcement ^[1].