Oral Compound Mic-628 Resets the Body Clock and Cuts Jet Lag Recovery Nearly in Half in Mice
A Japanese research team has identified a small molecule called Mic-628 that advances the mammalian circadian clock by activating the Period1 gene through a previously unexploited molecular pathway, cutting simulated jet lag recovery from seven days to four in mice after a single oral dose.
Overview
A multi-institutional Japanese research team has identified a small molecule that can reliably advance the mammalian body clock, offering a fundamentally different approach to resetting circadian rhythms compared with existing interventions such as light therapy or melatonin. The compound, designated Mic-628, shortened jet lag recovery from seven days to four days in mice after a single oral dose, according to ScienceDaily. The study was published in the Proceedings of the National Academy of Sciences on February 8, 2026.
The finding is notable because Mic-628 produces consistent clock-advancing effects regardless of when it is administered, a property that distinguishes it from melatonin and timed light exposure, both of which depend on precise dosing windows and often yield variable results.
How Mic-628 Works
The mammalian circadian clock is governed by a molecular feedback loop in which the proteins CLOCK and BMAL1 activate genes including Period1 (Per1) and Period2, whose protein products then accumulate and suppress their own transcription. The protein CRY1 plays a central role in this suppression, binding to the CLOCK-BMAL1 complex to silence clock gene activity.
Mic-628 exploits this machinery by binding directly to CRY1. Rather than blocking CRY1’s repressive function outright, the compound reconfigures the interaction: the resulting CLOCK-BMAL1-CRY1-Mic-628 complex activates Per1 transcription at a specific DNA regulatory element known as a dual E-box, according to the study published in PNAS. This targeted activation advances the phase of both the suprachiasmatic nucleus, the brain’s master pacemaker, and peripheral clocks in organs such as the lungs.
Mathematical modeling by the research team demonstrated that the compound’s stable, unidirectional phase-advancing effect arises from negative self-regulating feedback by the PER1 protein itself. Because PER1 eventually suppresses its own gene, the clock shifts forward by a defined amount and then stabilizes rather than spiraling into continuous acceleration.
Experimental Results
The researchers tested Mic-628 in a standard jet lag mouse model, subjecting animals to a six-hour advance of the light-dark cycle, equivalent to flying eastward across six time zones. Control mice required approximately seven days to fully re-entrain their activity rhythms to the new schedule. Mice that received a single oral dose of Mic-628 re-entrained in approximately four days, a reduction of nearly 43 percent, according to ScienceDaily.
A key finding was that the phase advance occurred regardless of when during the circadian cycle the compound was administered. Existing pharmacological approaches to circadian adjustment, including melatonin, are effective only within narrow time windows and can worsen misalignment if taken at the wrong time. The researchers described Mic-628 as “timing-proof,” a property that would simplify clinical use if the compound advances to human trials.
Research Team and Context
The study was led by Emeritus Professor Tei Hajime of Kanazawa University and included Associate Professor Takahata Yoshifumi of Osaka University, Professor Numano Rika of Toyohashi University of Technology, and Associate Professor Uriu Koichiro of the Institute of Science Tokyo, along with more than 20 additional co-authors, according to ScienceDaily.
The work builds on decades of research into the molecular clock, which earned Jeffrey Hall, Michael Rosbash, and Michael Young the 2017 Nobel Prize in Physiology or Medicine for their discovery of the Period gene in fruit flies. While the core clock mechanism is conserved across species, translating circadian biology into practical therapeutics has proven difficult. No drug currently approved by the U.S. Food and Drug Administration is specifically indicated for circadian rhythm phase adjustment.
Limitations and Next Steps
The study was conducted exclusively in mice, and animal circadian models do not fully replicate human physiology. Mice are nocturnal, and their re-entrainment dynamics differ from those of diurnal species. Safety, tolerability, and dose-response relationships remain unknown in humans.
The researchers have indicated plans for additional preclinical studies and eventual human trials. If Mic-628 or a derivative proves safe and effective in people, potential applications could extend beyond jet lag to shift-work disorder, delayed sleep-wake phase disorder, and other conditions rooted in circadian misalignment. Circadian disruption has been linked to elevated risks of metabolic disease, cardiovascular events, and cognitive decline, suggesting that a reliable clock-resetting tool could have broad clinical relevance.