Calico Life Sciences Announces European Medicines Agency Grants PRIME Designation to Investigational Fosigotifator for Vanishing White Matter

• PRIME designation granted based on preliminary clinical data from the ongoing Phase 1b/2 study and provides enhanced scientific and regulatory support from the EMA during fosigotifator's development
• Decision follows Breakthrough Therapy Designation from the U.S. Food and Drug Administration earlier this year
• There are currently no approved treatments for vanishing white matter, a rare, progressive, autosomal-recessive leukodystrophy

SOUTH SAN FRANCISCO, Calif., Oct. 22, 2026 /PRNewswire/ -- Calico Life Sciences LLC (Calico), a clinical-stage biotechnology organization focused on aging and age-related diseases and founded by Alphabet Inc. and Arthur D. Levinson, today announced that the European Medicines Agency (EMA) has granted PRIority MEdicines (PRIME) designation to fosigotifator, an investigational eIF2B activator being evaluated for the treatment of Vanishing White Matter (VWM). The designation was granted based on early clinical data from Calico's ongoing Phase 1b/2 clinical study (2023-505704-30-00) evaluating the safety, tolerability, pharmacokinetics, pharmacodynamics, and preliminary efficacy of fosigotifator in people with VWM.

"People living with Vanishing White Matter and their families urgently need therapies for this progressive condition," said Arthur D. Levinson, Ph.D., CEO of Calico. "PRIME designation reflects the significant unmet need in VWM, a disease with no approved treatments. We are encouraged by our preliminary data and look forward to working closely with the EMA as we continue to evaluate the safety and efficacy of investigational fosigotifator in our clinical studies."

The PRIME scheme is designed to provide enhanced support for the development of medicines that target conditions with an unmet medical need, for which no treatment option exists, or where they can offer a major therapeutic advantage over existing treatments. To be eligible for PRIME designation, a product candidate must show its potential to benefit patients with unmet medical needs based on early clinical data or on compelling non-clinical data and tolerability data from initial clinical trials.¹

The designation follows the U.S. Food and Drug Administration's (FDA) granting of Breakthrough Therapy Designation for fosigotifator earlier this year and builds on the program's prior selection for the FDA's Support for clinical Trials Advancing Rare disease Therapeutics (START) Pilot Program. These designations do not guarantee that fosigotifator will be approved.

About VWM

VWM is an ultra-rare, progressive, debilitating leukodystrophy—a disease of the brain's white matter—caused by variants in any of the five subunits of an essential enzyme in cells called eIF2B (EIF2B1–5). VWM-causing variants in eIF2B cause a reduction in enzymatic activity that leads to chronic activation of the integrated stress response (ISR).² 

In VWM, chronic activation of the ISR in the brain causes the white matter to degenerate. Individuals with VWM commonly experience symptoms such as ataxia and impaired gross and fine motor function, cognitive and behavioral deficits, seizures, and have a shortened lifespan.³ While 60% of people with VWM develop symptoms before 4 years of age, the age of onset varies and strongly predicts the disease course, including severe disability and mortality.³ The disease course is chronic and progressive, and stressors such as fever, infection, and mild head trauma may cause episodes of rapid deterioration. There is currently no cure and no treatment approved for VWM.⁴

About Fosigotifator

Developed by Calico, fosigotifator targets eIF2B, a translation initiation factor that is essential for protein synthesis and a key regulator of the ISR. Its development is part of Calico's broader research into ISR biology.

In preclinical studies in animal models, fosigotifator directly targets eIF2B and increases the activity of elF2B complexes carrying VWM-associated pathogenic variants. In these preclinical models, fosigotifator decreased the ISR in the brain and spinal cord and improved coordination and movement deficits, as well as extended lifespan.⁵ It is hypothesized that if proper function of the elF2B protein complex can be restored, brain white matter damage and loss may be prevented in people with VWM; this hypothesis is being evaluated in ongoing clinical studies and has not been established.

Fosigotifator is the first eIF2B activator that has been administered to people living with VWM. The global Phase 1b/2 clinical trial includes cohorts from infancy to adulthood.

Fosigotifator is an investigational drug. It has not been approved by the FDA, the EMA, or any other regulatory authority, and its safety and efficacy have not been established. PRIME and Breakthrough Therapy designations do not guarantee that fosigotifator will receive marketing authorization or approval, or that its development or review will be expedited.

About Calico

Calico (Calico Life Sciences LLC) is an Alphabet-founded research and development company whose mission is to harness advanced technologies and model systems to increase our understanding of the biology that controls human aging. Calico will use that knowledge to devise interventions that enable people to lead longer and healthier lives. To learn more about Calico, visit www.calicolabs.com. Follow @calico on LinkedIn, X, and YouTube.

1. PRIME: priority medicines | EMA (2026, October 21)
2. Yao Liang Wong, et al. eIF2B activator prevents neurological defects caused by a chronic integrated stress response. eLife 8:e42940 (2019)
3. Hamilton EMC, van der Lei HDW, Vermeulen G, et al. Natural history of vanishing white matter. Ann Neurol. 2018;84(2):274-288. 
4. Vanishing White Matter Consortium (2026, October 21)
5. Karin Lin, et al. Chronic integrated stress response causes dysregulated cholesterol synthesis in white matter disease. JCI Insight (2025)

SOURCE Calico Life Sciences LLC