Anti-inflammatory effect?
After reviewing the new findings, Frank Domino, MD, professor of family medicine and community health at the University of Massachusetts, Worcester, said he would encourage patients with high-risk COVID-19 to consider taking fluvoxamine to lower their risk of being hospitalized. “But I would make it clear this was not a ‘cure,’ “ he said, “and we are unsure how it helps.”
At this point, U.S. treatment guidelines do not recommend fluvoxamine as the standard of care for nonhospitalized COVID-19 patients, but the National Institutes of Health is “very aware of the data,” Dr. Sax told this news organization.
Fluvoxamine is a selective serotonin reuptake inhibitor (SSRI) – a class of drugs that includes the more commonly prescribed antidepressant fluoxetine (Prozac). If prescribed off-label to COVID-19 patients, fluvoxamine should not be used within 2 weeks of starting treatment with other SSRI or monoamine oxidase inhibitor antidepressants and should be used with caution with other QT-interval prolonging medications, Dr. Sax said.
In addition, fluvoxamine can enhance the effect of antiplatelet and anticoagulant drugs, potentially triggering bleeding.
On the basis of in vitro and mouse studies of fluvoxamine, “we think it has an anti-inflammatory effect,” said child psychiatrist Angela Reiersen, MD, of Washington University, St. Louis, who came up with the idea for testing fluvoxamine in last year’s phase 2 trial and coauthored a recent article describing the drug’s potential mechanisms of action in COVID-19.
She and other researchers believe fluvoxamine’s anti-inflammatory effects derive from the molecule’s binding to the sigma-1 receptor in the endoplasmic reticulum, which regulates cellular responses to stress and infection.
Fluvoxamine also inhibits the activation of platelets. “In COVID-19, there does seem to be a problem with hyperactivation of platelets and excessive blood clots forming, so it is possible this could be another mechanism where it might be helping,” Dr. Reiersen said.
If sigma-1 activation turns out to be the main mechanism underlying fluvoxamine’s benefits in COVID-19, other sigma-1 agonists, such as fluoxetine, may also help. In a retrospective analysis of thousands of adults hospitalized for COVID-19 in France early in the pandemic, those who were taking antidepressants had a 44% lower risk for intubation or death.
And in a study under review, researchers at Stanford (Calif.) University and the University of California, San Francisco, analyzed electronic health records to explore a potential link between fluoxetine use and COVID outcomes among more than 80,000 patients from over 80 institutions across the United States. Other research suggests that antipsychotics could also have protective effects for patients with COVID-19.
Long COVID, long-term challenges
On the basis of its potential mechanisms of action, fluvoxamine may be able to prevent or treat long COVID, Dr. Reiersen said. That possibility will be assessed among other secondary endpoints in two ongoing studies of repurposed drugs: the NIH’s ACTIV-6, and the University of Minnesota’s COVID-OUT, an at-home trial of ivermectin, metformin, and fluvoxamine.
Dr. Reiersen and Washington University colleagues are also analyzing longer-term outcomes of participants in their own phase 3 trial of fluvoxamine (Stop COVID 2), which was discontinued when enrollment slowed to a trickle during the U.S. vaccine rollout. Logistical hurdles and scant funding have greatly hampered efforts to test the use of off-patent drugs for COVID-19 outpatients during the pandemic.
U.S. efforts face other obstacles as well. Elsewhere in the world – including Brazil, where the TOGETHER trial was run – vaccines are scarce, and there are no monoclonal antibodies.
“People have a great sense of community duty, and they’re participating in the trials,” Dr. Mills said. “You’re in a much more political environment in the U.S. on these outpatient trials.”
The TOGETHER trial was funded by Fast Grants and the Rainwater Foundation. Dr. Reiersen is an inventor on a patent application related to methods of treating COVID-19, which was filed by Washington University, St. Louis. Dr. Mills, Dr. Domino, and Dr. Sax report no relevant financial relationships.
A version of this article first appeared on Medscape.com.