PridCor Therapeutics advances Phase 2 SHIELD Long COVID study
PridCor Therapeutics has moved its SHIELD study of a triple-drug antiviral regimen for Long COVID closer to the clinic, making the first payment under its clinical trial agreement with the Icahn School of Medicine at Mount Sinai and confirming that study drug has been ordered. Preliminary screening of potential participants has begun at Mount Sinai's Cohen Center for Recovery from Complex Chronic Illness, with formal patient enrolment to follow once drug supplies are in place.
SHIELD (SARS-CoV-2 and Herpesvirus Inhibition for Ending Long COVID Dysfunction) is a randomised, double-blind, placebo-controlled Phase 2 study registered on ClinicalTrials.gov as NCT07597902. It is designed to enrol approximately 150 adults aged 18 to 65 and will evaluate a combination of valacyclovir, celecoxib, and a 25-day course of nirmatrelvir/ritonavir (marketed by Pfizer as Paxlovid) against matched placebo over a 14-week treatment period.
The scientific rationale
The regimen is constructed to address two hypothesised mechanisms driving Long COVID simultaneously: persistent SARS-CoV-2 viral reservoir, targeted by nirmatrelvir/ritonavir, and reactivation of latent herpesviruses, addressed by the valacyclovir and celecoxib combination. Each of the three drugs is individually FDA-approved for other indications; their use in combination for Long COVID is investigational and has not been approved. Notably, the FDA has confirmed in writing that the study meets criteria for exemption from an IND application, meaning SHIELD is exploratory and its results are intended to inform the design of any future IND-supported study rather than to support a regulatory submission directly.
The study follows a peer-reviewed open-label case series published in Frontiers in Immunology in January 2026, led by PridCor co-founder William Pridgen and Mount Sinai's David Putrino. In that 24-patient series, participants receiving the three-drug regimen reported a mean Patient Global Impression of Change score for fatigue of 6.8 on a seven-point scale, compared with 4.8 in those receiving valacyclovir and celecoxib alone (p less than 0.0001). Improvements were reported as sustained at follow-up points beyond 300 days. The authors themselves noted the series was small, open-label, and single-site, and called for a randomised controlled trial as the necessary next step.
The primary endpoint for SHIELD is the EQ-5D-5L visual analogue scale, on which participants rate overall health from 0 to 100, assessed at multiple time points up to week 20. Secondary measures include the PROMIS-29, GSQ-30, and Neuro-QoL Cognitive Function instruments, along with standardised assessments of mood, anxiety, and sleep. David Putrino, Professor of Rehabilitation and Human Performance at Mount Sinai, is serving as principal investigator, with Amy Proal of the PolyBio Research Foundation as co-investigator.
"SHIELD is designed to tell us whether what we observed holds up under blinding and against a placebo arm, and people living with Long COVID deserve that answer," said William Pridgen, co-founder and chief executive of PridCor Therapeutics.
Market context
Long COVID represents one of the largest unmet needs in post-infectious disease, with an estimated 400 million people affected on a cumulative basis worldwide and an annual economic burden cited in published literature at approximately one trillion US dollars. No treatments are currently FDA-approved for the condition. That regulatory vacuum has drawn increasing attention from academic consortia, government-funded research programmes such as the NIH RECOVER initiative, and a growing number of small biotechs and spinouts exploring antiviral, anti-inflammatory, and autonomic approaches. PridCor's repositioning of approved antivirals and anti-inflammatory agents is a relatively low-cost entry strategy compared with novel-drug development, though the IND-exempt, exploratory status of SHIELD also means commercial and regulatory pathways remain undefined. Readout of the 20-week endpoint data will be the key milestone to watch, as it will determine whether a larger, IND-supported pivotal programme is warranted.