The world's first fridge-free vaccine has produced encouraging Phase I results, offering a potential route to reducing the number of vaccines lost each year globally to cold-chain failures during storage and transport.
SPVX02, a reformulated tetanus-diphtheria (Td) vaccine developed by UK biotech Stablepharma, was tested in a randomised Phase I trial involving 60 healthy adults at the NIHR Clinical Research Facility at University Hospital Southampton.
The results, published in eClinicalMedicine, showed the vaccine was well tolerated with no vaccine-related serious adverse events and that by 28 days all participants had reached protective antibody levels against both tetanus and diphtheria, comparable to licensed vaccines.
Critically, stability data showed that SPVX02 retains potency for at least two years when stored at 30°C (and for six months under accelerated conditions at 40°C).
Testing is ongoing to establish whether stability can be extended to four years.
The vaccine has also been shown to remain fully potent after three cycles of extreme temperature fluctuation between -20°C and +40°C.
How the platform works
SPVX02 is built on Stablepharma's StablevaX platform, which converts products normally requiring 2-8°C refrigeration into room-temperature-stable formulations.
Speaking to Manufacturing Chemist, Stablepharma COO Dr Karen O'Hanlon (pictured) explained that the platform reformulates products using a proprietary blend of trehalose and other GRAS excipients, followed by a drying process, typically lyophilisation.
"[This] creates stable, solid formulations that can be reconstituted, typically with sterile water, immediately before administration to a patient," she said.
The approach immobilises both the vaccine antigen and the aluminium-containing adjuvant in a solid, glass-like state, preventing the particle aggregation and toxoid degradation that normally occur when vaccines are exposed to heat or freezing.
According to Dr O'Hanlon, this is a significant technical achievement given that aluminium hydroxide adjuvant has historically been one of the most challenging vaccine formats to thermostabilise.
Converting the liquid Td vaccine into a lyophilised format brought several manufacturing hurdles, she added, including protecting the toxoid antigens during drying, preventing degradation of the aluminium hydroxide adjuvant and ensuring the process was compatible with standard equipment used across global vaccine manufacturing.
These challenges were overcome by our own experienced formulation scientists who worked diligently to develop a durable, robust, pilot-scale manufacturing process in their lab in Madrid.
"We then successfully tech-transferred to ThermoFisher in Italy for the production of the GMP batches needed for our clinical trials," she stated.
The stability programme monitors 21 critical quality attributes, including potency, antigen identity, aluminium content, residual moisture, sterility and reconstitution performance, with data so far described by Dr O'Hanlon as consistent across both long-term and accelerated storage conditions.
Wider pipeline
Stablepharma has since launched a Phase IIb trial, approved in June 2026, to assess SPVX02 in a larger cohort.
The company said it is now evaluating other candidates for the StablevaX platform, including hepatitis B and HPV vaccines, based on technical fit, market need and partner interest.
SPVX02 has now demonstrated that StablevaX can successfully thermostabilise an aluminium-adjuvanted vaccine and the Phase I clinical data allows us to now open up opportunities across a wide range of inactivated, toxoid and other adjuvanted vaccines.
The platform is also being applied beyond vaccines: Stablepharma is working with partners in Madrid to thermostabilise small-molecule oncology and anti-infective products.
Stablepharma CEO Özgür Tuncer said the trial outcome marks "a pivotal moment for our StablevaX platform and the future of thermostable vaccines."
SPVX02 was developed with support from Innovate UK (UKRI), with specialist laboratory testing from the UK Health Security Agency.
Stablepharma expects to complete SPVX02's clinical development programme by 2027.
