Elasomeran Mechanism of Action: How Elasomeran Works | Elicit
Elasomeran Mechanism of Action
How Elasomeran (Spikevax) Works: mRNA/LNP delivery codes for pre-fusion stabilized SARS-CoV-2 spike protein, leading to S antigen expression and protective immune responses.
Last updated:
March 2026
Quick Summary
Elasomeran (Spikevax) is an mRNA vaccine used for the prevention of COVID-19 caused by SARS-CoV-2. It uses synthetic nucleoside-modified mRNA encapsulated in lipid nanoparticles to deliver instructions for the full-length, pre-fusion stabilized SARS-CoV-2 spike (S) protein. After vaccination, human cells express the spike antigen and an immune response is elicited, leading to protection against SARS-CoV-2.
Properties
| Details | |
|---|---|
| Generic Name | Elasomeran |
| Brand Names | COVID-19 Vaccine Moderna, Spikevax |
| Drug Class | mRNA vaccine |
| Primary Target | SARS-CoV-2 spike (S) protein antigen |
| Approved Indications | Active immunization to prevent COVID-19 caused by SARS-CoV-2 in individuals ≥6 months of age |
| Key Effect | Encodes SARS-CoV-2 spike (S) antigen expression to elicit an immune response that leads to protection against SARS-CoV-2. |
Development History
Elasomeran was developed by Moderna in partnership with the U.S. National Institute of Allergy and Infectious Diseases (NIAID) Vaccine Research Center, building on a decade of structure-based immunogen design for class I viral fusion glycoproteins. The molecule is a nucleoside-modified mRNA, encapsulated in a lipid nanoparticle, that encodes the full-length SARS-CoV-2 spike protein locked in its prefusion conformation by two proline substitutions (K986P/V987P). The pivotal evidence supporting first approval came from the Phase 3 Coronavirus Efficacy (COVE) trial, a placebo-controlled study that randomized approximately 30,000 adults to two 100 µg intramuscular doses 28 days apart. The trial reported 94.1% efficacy against symptomatic disease.
Detailed Mechanism of Action
Lipid nanoparticle delivery and cellular entry. Elasomeran (mRNA-1273) is administered by intramuscular injection, where its nucleoside-modified mRNA is encapsulated in a lipid nanoparticle (LNP). The vaccine triggers a transient localized inflammatory response, and recruits monocytes, macrophages, and dendritic cells to the injection site.
Spike protein expression. Once LNPs are internalized and undergo endosomal escape, the mRNA encodes the full-length SARS-CoV-2 spike (S) protein with proline substitutions, which stabilize the protein in the prefusion conformation.
Antigen presentation and initial innate signaling. Following translation and processing, the spike protein is degraded in the cytoplasm, enabling direct CD8⁺ T cell priming.
N1-methylpseudouridine substitution and innate immune evasion. Each uridine in elasomeran's mRNA is replaced by N1-methylpseudouridine (m1Ψ), which reduces activation of TLR3, TLR7, and TLR8 and interferon responsiveness.
Adaptive immune cascade. Nucleoside-modified mRNA-LNP platforms induce high levels of T follicular helper (Tfh) cells and germinal center (GC) B cells, associated with long-lived, high-affinity neutralizing antibodies.
Clinical translation. In the phase 3 COVE trial, vaccine efficacy in preventing COVID-19 illness was 93.2%.
Clinical Relevance
Approved Indications
- COVID-19 Primary Series (Adults ≥18 Years): 94.1% efficacy against symptomatic COVID-19.
- Pediatric Extension (Ages 6 Months–17 Years): FDA authorization expanded Spikevax to children as young as 6 months.
- Variant-Adapted Boosters: Updated monovalent formulations (XBB.1.5)
Key Drug Interactions
- Immunosuppressive Therapy: Diminished antibody responses in transplant recipients.
- Anticoagulants (Procedural): Risk of injection-site hematoma.
Myocarditis and Pericarditis Warning
- Post-Dose Risk in Young Males: Increased risk reported in males 12–24 years of age.
Emerging Indications
Elasomeran is a single-indication vaccine targeting COVID-19, with no Phase 2 or later clinical trials in non-COVID therapeutic areas.
Oncology
- Melanoma / Adjuvant Therapy (Phase 2b/3, active): Individualized neoantigen therapy using the mRNA-LNP platform.
Clinical Trials of Elasomeran
| Trial Name | Phase Design | N Enrolled | Intervention | Indication | Primary Endpoint | Key Result | Status |
|---|---|---|---|---|---|---|---|
| COVE (2020-2022) | Phase 3 RCT | 30420 | Two 100 mcg doses of mRNA-1273 vs. placebo | COVID-19 Prevention in Adults >=18 Years | Prevention of symptomatic COVID-19 with onset at least 14 days after the second injection | 94.1% efficacy against symptomatic COVID-19. Completed | Completed |
Open Research Questions
What are the mechanistic determinants of vaccine-associated myocarditis?
To what extent does elasomeran induce functional mucosal IgA at the respiratory epithelium?
What is the mechanism by which prior SARS-CoV-2 infection modulates humoral responses to subsequent elasomeran vaccination?
How do CD8+ T-cell responses to elasomeran vary by age and immunocompetence?
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This mechanism of action page was generated using Elicit's AI research agent, which synthesizes explanations from peer-reviewed pharmacology literature.