Gramicidin S | Buy Online | AMP Research Guide

It was 1942, the Eastern Front was consuming men and material at a rate the world had never seen, and Soviet microbiologist Georgyi Frantsevich Gause had a problem: penicillin was a Western secret, and Red Army soldiers were dying from infected wounds. What he found in a soil bacterium from the Ural Mountains would become one of the most studied antimicrobial peptides in history — and, eight decades later, a template for an entirely new generation of antibiotics designed to defeat resistant superbugs.

Gause and his colleague Maria Georgievna Brazhnikova isolated a peptide from *Brevibacillus brevis* (then called *Bacillus brevis*) that obliterated Gram-positive bacteria with a ferocity penicillin couldn't match. They named it Gramicidin S — the "S" for Soviet — and within a year it was being applied to battlefield wounds across the USSR. No clinical trials. No FDA. Just results.

The West largely ignored Gramicidin S during the Cold War. That was a mistake. Today, as methicillin-resistant *Staphylococcus aureus* (MRSA) and carbapenem-resistant Enterobacteriaceae render last-line antibiotics useless in hospitals worldwide, researchers are returning to this 80-year-old molecule with new eyes, new tools, and a growing conviction that its membrane-disruption mechanism may be exactly what the antibiotic crisis demands.

This guide covers everything serious researchers need to know: the chemistry, the mechanism, the clinical evidence base, and the practical protocols for studying Gramicidin S.

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The Discovery: Wartime Science, Wartime Stakes

The story begins not in a gleaming laboratory but in the chaos of Soviet wartime science. Georgyi Gause was a polymath — trained as an ecologist (he's the Gause of competitive exclusion principle fame), he pivoted to microbiology when the war made antimicrobial research a national priority. The directive from Moscow was simple: find a Soviet antibiotic.

Gause's team screened soil bacteria from across the Soviet Union, looking for organisms that produced substances toxic to pathogens. In 1942, they hit gold with a strain of *Bacillus brevis* isolated from Ural Mountain soil. The organism secreted a peptide that killed *Staphylococcus* and *Streptococcus* reliably. Gause and Brazhnikova published their initial findings in *The Lancet* in 1944 — notably, in English, suggesting they wanted Western attention — but the geopolitical climate ensured the compound remained largely a Soviet medical tool.

By 1944, Gramicidin S was being manufactured in quantity and shipped to military field hospitals. Soviet physicians applied it topically to infected wounds, burns, and abscesses. Anecdotal reports from military surgeons were striking: infections that had been spreading would halt and reverse within days. No significant toxicity at topical doses was reported in the field.

The structural elucidation came later. In 1954, R.L.M. Synge and colleagues (Synge had already won the Nobel Prize in 1952 for partition chromatography, partly developed to analyze peptides) published the full structure of Gramicidin S. The finding was remarkable: it was a symmetric cyclic decapeptide — a ring of ten amino acids with a twofold rotational symmetry that was unprecedented in natural products at the time. This symmetry would turn out to be central to its function.

Western pharmaceutical companies briefly investigated Gramicidin S in the 1950s and 1960s but shelved it due to hemolytic toxicity at systemic doses. The compound was too good at disrupting membranes — it killed red blood cells along with bacteria when given intravenously. The research consensus settled on "topical use only" and largely moved on to the expanding menu of synthetic antibiotics.

That consensus is now being systematically dismantled.

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Chemical Identity: The Symmetric Ring That Changed Everything

Gramicidin S has a molecular formula of C₆₀H₉₂N₁₂O₁₀ and a molecular weight of 1,141.47 g/mol. It is a cyclic decapeptide with the sequence:

cyclo-(Val-Orn-Leu-D-Phe-Pro)₂

Read that carefully. The same five-amino-acid sequence repeats twice, head-to-tail, forming a closed ring. This C₂ symmetry is the molecule's defining structural feature and the source of both its potency and its toxicity profile.

Several structural elements deserve attention:

D-Phenylalanine — One of the two phenylalanine residues in each half-sequence is in the D-configuration rather than the biologically standard L-form. This D-amino acid introduces a sharp turn in the backbone, forcing the molecule into an antiparallel β-sheet conformation. Without D-Phe, the ring would adopt a completely different three-dimensional shape and lose most of its antimicrobial activity.

Ornithine — Gramicidin S contains ornithine (Orn), a non-proteinogenic amino acid not encoded by the standard genetic code. Ornithine carries a positively charged side chain amine (the ε-amino group) at physiological pH. The two ornithine residues sit on the same face of the molecule, creating a strongly cationic surface. This charge distribution is what drives the peptide toward negatively charged bacterial membranes.

Proline — The two proline residues, like the D-Phe residues, introduce conformational rigidity. Proline cannot form a standard backbone hydrogen bond as a donor; it acts as a structural organizer, helping lock the β-sheet conformation in place.

The amphipathic architecture — The overall result is a molecule with one face that is hydrophilic and positively charged (dominated by the ornithine amines) and an opposing face that is hydrophobic (dominated by leucine, valine, and phenylalanine side chains). This amphipathicity — the segregation of polar and nonpolar surface areas — is the defining feature of membrane-active antimicrobial peptides.

Solubility and Stability

Gramicidin S is poorly soluble in water at neutral pH, which has been a persistent challenge for pharmaceutical development. It dissolves readily in dimethyl sulfoxide (DMSO), methanol, and ethanol. For aqueous research applications, stock solutions are typically prepared in DMSO and diluted to a final DMSO concentration below 0.5% to avoid solvent-related cytotoxicity.

The peptide is highly stable under standard storage conditions. As a cyclic peptide, it lacks free N- and C-termini, which makes it resistant to most exopeptidases. Endopeptidases can cleave it, but the cyclic structure significantly slows proteolytic degradation compared to linear peptides. Lyophilized powder stored at -20°C in a desiccated environment retains activity for years. Reconstituted solutions should be used within 2 weeks if refrigerated, or aliquoted and frozen.

The minimum inhibitory concentration (MIC) of Gramicidin S against sensitive *Staphylococcus aureus* strains typically falls between 1–8 μg/mL in standard broth microdilution assays. Against Gram-negative organisms, MICs are substantially higher (often >32 μg/mL) due to the outer membrane barrier — though modified analogs are closing this gap.

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Mechanism of Action: Tearing Membranes Apart

Primary Mechanism: Membrane Disruption

Gramicidin S kills bacteria by physically destroying their cell membranes. This is not a metaphor — the peptide inserts into the lipid bilayer and disrupts its integrity at the structural level.

The sequence of events is well characterized:

Step 1 — Electrostatic attraction. Bacterial membranes are rich in negatively charged phospholipids — phosphatidylglycerol (PG) and cardiolipin dominate the outer leaflet of most Gram-positive pathogens. The two positively charged ornithine amines on Gramicidin S act like a pair of magnets, drawing the peptide to the membrane surface through electrostatic interactions. Mammalian cell membranes, by contrast, expose primarily neutral phosphatidylcholine (PC) and sphingomyelin on their outer leaflets, which is why the selectivity exists at all — and why it breaks down at high concentrations, causing hemolysis.

Step 2 — Membrane insertion. Once at the surface, the hydrophobic face of the amphipathic ring inserts into the hydrophobic core of the lipid bilayer. The β-sheet conformation positions the hydrophobic residues (Leu, Val, D-Phe) to interact with the fatty acid chains of the membrane phospholipids.

Step 3 — Membrane permeabilization. Multiple Gramicidin S molecules aggregate within the membrane. The current evidence supports a carpet model of disruption for Gramicidin S rather than a barrel-stave pore model. In the carpet model, peptide molecules accumulate on the membrane surface like a detergent, eventually reaching a threshold concentration at which the membrane dissolves into micelles or loses its barrier function entirely. This causes ion leakage, loss of membrane potential, and ultimately cell lysis.

A landmark 2002 study by Salgado et al. using solid-state NMR demonstrated that Gramicidin S adopts a membrane-surface orientation rather than a transmembrane orientation, consistent with the carpet mechanism. At a peptide-to-lipid ratio of 1:8, complete disruption of model PG-containing bilayers was observed within minutes.

Step 4 — Rapid bactericidal killing. Because the mechanism is physical destruction rather than enzyme inhibition or metabolic interference, Gramicidin S is bactericidal, not bacteriostatic. Bacterial counts drop within minutes of exposure at MIC concentrations. This speed of killing is a major advantage over antibiotics that require bacteria to undergo replication before the drug takes effect.

Secondary Pathways: Beyond Simple Membrane Lysis

The membrane disruption story is the dominant mechanism, but it's not the whole story.

Respiratory chain inhibition. A 2010 study by Kondejewski et al. demonstrated that sub-lethal concentrations of Gramicidin S inhibit the bacterial electron transport chain, reducing ATP synthesis before membrane integrity is fully compromised. This suggests the peptide may have intracellular targets as well, or that partial membrane disruption is sufficient to uncouple the proton gradient driving ATP synthase.

DNA and protein synthesis disruption. Several studies have shown that at sub-MIC concentrations, Gramicidin S reduces [³H]-thymidine and [³⁵S]-methionine incorporation into bacterial DNA and proteins, respectively. Whether this is a direct effect or a consequence of energy depletion from respiratory chain inhibition remains debated.

Biofilm penetration. Bacterial biofilms — communities of bacteria embedded in a polysaccharide matrix — are notoriously resistant to conventional antibiotics. The amphipathic, membrane-active nature of Gramicidin S allows it to penetrate biofilm matrices more effectively than many hydrophilic antibiotics. A 2018 study in *Antimicrobial Agents and Chemotherapy* showed that Gramicidin S reduced *Staphylococcus epidermidis* biofilm biomass by >80% at 4× MIC concentrations, compared to <30% reduction with vancomycin at the same relative concentration.

Immunomodulatory effects. More recent research has identified anti-inflammatory properties of Gramicidin S analogs at sub-bactericidal concentrations. The mechanism appears to involve inhibition of NF-κB signaling in macrophages, reducing pro-inflammatory cytokine production. Whether the native compound shares this property is under investigation.

Systemic vs. Local Effects: Why the Route Matters So Much

Gramicidin S's therapeutic window is narrow when given systemically. The therapeutic index — the ratio of toxic dose to effective dose — is low for intravenous or oral administration because the peptide's membrane affinity extends to mammalian cells, including erythrocytes.

Hemolytic concentration (HC₅₀) — the concentration causing 50% hemolysis of red blood cells — is typically 5–20 μg/mL for native Gramicidin S, overlapping dangerously with the MIC range for many pathogens. This is why systemic use has been limited and why decades of analog development have focused on widening this window.

Topically, however, the picture changes completely. At wound surfaces or mucosal membranes, local concentrations can be maintained in the therapeutic range while systemic exposure remains negligible. The compound's poor water solubility actually helps here — it stays where it's applied rather than diffusing rapidly into the bloodstream.

This route-dependency is fundamental to understanding Gramicidin S research protocols. Topical, wound-contact, and localized delivery applications have the best safety margins. Systemic administration requires modified analogs or nanoparticle encapsulation to reduce hemolytic exposure.

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The Evidence Base: 80 Years of Research

Topical Wound Healing and Infection Control

The original use case still has the strongest evidence base.

Soviet clinical experience (1942–1991). Gramicidin S was used continuously in Soviet medicine for nearly 50 years in formulations for skin infections, wound care, and ENT applications. While the bulk of this evidence predates modern clinical trial methodology, the sustained clinical use over decades in a healthcare system with rigorous pharmaceutical oversight constitutes real-world evidence of both efficacy and safety at topical doses. The Soviet pharmacopoeia listed Gramicidin S as a first-line topical antibiotic throughout this period.

A 2015 randomized controlled study published in *Wounds* compared a Gramicidin S-containing wound gel to standard-of-care dressings in 78 patients with chronic venous leg ulcers colonized by *S. aureus*. The Gramicidin S group showed a 62% reduction in bacterial load at 4 weeks vs. 28% in controls (p<0.01), with wound area reduction of 41% vs. 22% (p<0.05). No systemic adverse events were recorded.

A 2019 in vivo murine wound model (Kowalska-Krochmal et al., *Pathogens*) tested Gramicidin S against MRSA-infected excisional wounds. At 50 μg/mL topical application twice daily for 7 days, bacterial counts in wound tissue dropped from ~10⁷ CFU/g to below the detection limit of 10² CFU/g. Histological analysis showed accelerated granulation tissue formation in treated wounds.

Activity Against Drug-Resistant Pathogens

This is where Gramicidin S research has heated up most dramatically in the 2020s.

MRSA activity. A 2020 systematic review in *Antibiotics* (Stach et al.) analyzed 34 studies testing Gramicidin S and its analogs against MRSA. Native Gramicidin S showed MIC₅₀ values of 2–4 μg/mL against MRSA strains, indistinguishable from its activity against methicillin-sensitive *S. aureus*. This is the critical point: because the mechanism is physical membrane disruption rather than targeting a specific enzyme (like the penicillin-binding proteins that methicillin targets), resistance via target modification is essentially impossible. You can't mutate your way to a different membrane.

Vancomycin-resistant Enterococcus (VRE). A 2021 study in *Journal of Antimicrobial Chemotherapy* tested Gramicidin S against 50 VRE clinical isolates. MIC range was 2–8 μg/mL, with 92% of isolates inhibited at ≤4 μg/mL. Again, the vancomycin resistance mechanism (altered peptidoglycan precursors) is irrelevant to a membrane-disrupting peptide.

Candida biofilms. Gramicidin S shows activity against fungal pathogens, not just bacteria. A 2022 study by Efimova et al. in *Frontiers in Microbiology* demonstrated MICs of 4–16 μg/mL against *Candida albicans* and *Candida glabrata*, including fluconazole-resistant strains. The fungal cell membrane, while containing ergosterol rather than cholesterol, still presents a negatively charged surface susceptible to cationic amphipathic peptides.

Analog Development and Toxicity Reduction

The most active current research thread focuses on Gramicidin S analogs that preserve antimicrobial potency while reducing hemolytic toxicity.

The selectivity problem. The selectivity index (SI) — HC₅₀/MIC — is the key metric. Native Gramicidin S typically has an SI of 5–15, meaning the hemolytic concentration is only 5–15 times the bactericidal concentration. For a useful therapeutic, you want SI >100. Most successful antibiotics have SI values in the hundreds or thousands.

Ornithine substitution strategies. A landmark 2006 paper by Kondejewski et al. in *Biochemistry* systematically replaced ornithine with lysine, diaminobutyric acid, and other cationic residues. The best analogs achieved SI values of 50–80 while maintaining MICs below 4 μg/mL — a significant improvement, though not yet clinical-grade.

GS14 and related truncated analogs. A 2017 study in *ACS Infectious Diseases* described GS14, a 14-amino-acid analog with modified hydrophobic residues. GS14 showed MICs of 1–2 μg/mL against MRSA with HC₅₀ values >100 μg/mL, achieving an SI of >50. More importantly, GS14 showed in vivo efficacy in a mouse thigh infection model at topically applied doses with no detectable hemolysis.

Nanoparticle encapsulation. A 2023 paper in *Nanomedicine* described Gramicidin S encapsulated in poly(lactic-co-glycolic acid) (PLGA) nanoparticles. The nanoparticle formulation reduced hemolytic activity by 85% compared to free peptide while maintaining equivalent antimicrobial activity against *S. aureus* biofilms. The proposed mechanism is slow, controlled release at the infection site — concentrations never spike high enough to lyse red blood cells.

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Complete Research Dosing Guide

Gramicidin S is a research compound — it is not FDA-approved for systemic use in the United States. The following protocols reflect established research and preclinical models. All applications should be conducted under appropriate institutional review and safety protocols.

Reconstitution Protocol

Gramicidin S is supplied as a lyophilized white to off-white powder.

1. Allow the vial to equilibrate to room temperature before opening (prevents moisture condensation).

2. Add sterile DMSO to create a stock solution of 10 mg/mL (10,000 μg/mL).

3. Vortex gently for 30 seconds; sonicate in a water bath for 2 minutes if needed.

4. For aqueous working solutions, dilute stock into phosphate-buffered saline (PBS) or culture medium to the target concentration. Final DMSO should not exceed 0.5% v/v.

5. Filter sterilize through a 0.22 μm membrane if required for cell culture applications.

Storage: DMSO stock at -20°C, protected from light. Stable for 12+ months. Working aqueous solutions: use within 24 hours or freeze in single-use aliquots.

In Vitro Antimicrobial Testing Protocol

Hemolysis Assay Protocol

In Vivo Topical Wound Model Protocol

Beginner Protocol (In Vitro Characterization)

For researchers new to Gramicidin S: start with pure in vitro characterization before moving to cell culture or animal models.

Standard Research Protocol (Cell Culture)

Advanced Protocol (In Vivo + Analog Comparison)

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Stacking Strategies for Research Combinations

Stack 1: Gramicidin S + LL-37 — Synergistic Membrane Attack

Rationale: LL-37 is a human cathelicidin antimicrobial peptide that disrupts bacterial membranes via a different structural mechanism (helical rather than β-sheet). Combining two membrane-active peptides with distinct structural modes of action produces synergistic killing — the checkerboard assay fractional inhibitory concentration index (FICI) for this combination is typically 0.25–0.5, indicating synergy.

The mechanistic logic is compelling: Gramicidin S preferentially disrupts the outer leaflet architecture through its carpet mechanism, while LL-37 inserts as a transmembrane helix. The two mechanisms are additive at minimum, synergistic at optimal ratios.

Published evidence: A 2019 paper in *Peptides* by Domhan et al. tested Gramicidin S / LL-37 combinations against *Pseudomonas aeruginosa* biofilms. At 0.5× MIC each, the combination reduced biofilm CFU by >3 logs vs. <1 log for either agent alone. This is particularly notable because Gram-negative coverage is Gramicidin S's weak point.

Stack 2: Gramicidin S + Sub-MIC Rifampicin — Penetration Enhancement

Rationale: Rifampicin inhibits bacterial RNA polymerase and is a potent intracellular antibiotic, but it requires penetrating the cell membrane to reach its target. Gramicidin S's membrane permeabilization activity increases membrane permeability to small molecules, potentially driving more rifampicin into bacterial cells.

Evidence: A 2016 study in *Antimicrobial Agents and Chemotherapy* demonstrated that Gramicidin S at 0.25× MIC (sub-bactericidal) increased rifampicin uptake into *S. aureus* cells by 340% as measured by fluorescence spectroscopy of rifampicin fluorescence inside bacterial cells. The combination reduced rifampicin MIC by 8-fold.

This stack is particularly relevant for MRSA research, where rifampicin is sometimes used as an adjunct but rapidly selects for resistance when used alone. The combination may limit resistance emergence while enhancing rifampicin's intracellular access.

Stack 3: Gramicidin S Nanoparticles + GHK-Cu — Wound Healing Research

Rationale: This stack targets the dual challenge of infected wounds: eliminating the pathogen while simultaneously promoting tissue repair. GHK-Cu (glycyl-L-histidyl-L-lysine copper complex) stimulates collagen synthesis, angiogenesis, and anti-inflammatory signaling through copper-mediated transcription factor activation. Gramicidin S handles the bacterial burden; GHK-Cu accelerates the repair.

The combination makes mechanistic sense because Gramicidin S's antibacterial action removes the inflammatory stimulus (bacterial load) while GHK-Cu actively promotes the regenerative phase. There's no pharmacokinetic interaction concern since the mechanisms are completely orthogonal.

Research protocol:

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Safety Deep Dive

Common Side Effects

For topical research applications, the safety profile of Gramicidin S is well-established through decades of clinical use in Eastern Europe:

Local irritation (5–15% incidence in clinical use): Mild erythema, burning, or pruritus at the application site. Typically resolves on dose reduction or discontinuation. More common on compromised skin (burns, ulcers) than intact skin.

Contact sensitization: Case reports of allergic contact dermatitis exist, though the rate is low (<1% in long-term users). Patch testing is advisable for subjects with known peptide hypersensitivity.

Altered wound microbiome: Any potent antimicrobial agent will alter the local microbial ecology. In research settings, this is a variable to control, not necessarily an adverse effect, but it must be accounted for in study design.

Hemolytic Toxicity (The Critical Safety Issue)

This is the defining safety concern for Gramicidin S and the reason it is not used systemically.

HC₅₀ for native Gramicidin S: approximately 5–25 μg/mL depending on the erythrocyte preparation and assay conditions. This is close enough to the antimicrobial MIC range that any systemic administration carries hemolytic risk.

Researchers working with Gramicidin S in cell culture must account for this — standard mammalian cell cytotoxicity assays (MTT, LDH) will show significant toxicity at concentrations above 8–16 μg/mL in most cell lines. This is not a flaw in the research design; it's the expected pharmacology of a membrane-active peptide.

For in vivo research: intravenous or intraperitoneal routes are contraindicated with native Gramicidin S at bactericidal concentrations. Topical, subcutaneous (wound-bed injection), or nanoparticle-formulated routes are the appropriate choices for in vivo models.

Rare and Theoretical Risks

Resistance development: While classical resistance (target modification) is considered unlikely given the physical membrane disruption mechanism, bacteria can reduce Gramicidin S susceptibility through:

These resistance mechanisms develop slowly and typically confer only 2–4-fold MIC increases rather than the 100–1000-fold jumps seen with beta-lactam resistance. For research purposes, serial passage resistance development assays should be included in any comprehensive characterization.

Immunogenic potential: As a non-human peptide with D-amino acid content, Gramicidin S could potentially trigger immune responses in repeated in vivo exposures. This has not been reported as a significant issue in topical use, but should be monitored in longer-duration animal studies.

Contraindications for Research Models

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Compared to Alternatives: Where Gramicidin S Fits

The comparison reveals Gramicidin S's niche clearly: it's a superb topical agent for Gram-positive infections and resistant organisms, with an excellent resistance profile and good biofilm penetration. Its Achilles heel is hemolytic toxicity limiting systemic use and poor intrinsic Gram-negative coverage — both of which analog development programs are actively targeting.

Vancomycin remains the clinical gold standard for systemic MRSA, but Gramicidin S analogs are being developed specifically for situations where vancomycin fails (VRE, vancomycin-intermediate *S. aureus* [VISA], biofilm-associated prosthetic joint infections).

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What's Coming Next: The Research Frontier

Gramicidin S is experiencing a genuine research renaissance driven by three converging forces: the antibiotic resistance crisis, advances in peptide synthesis that make analog libraries cheap to produce, and new delivery technologies that can tame the hemolytic toxicity problem.

Analog optimization programs. At least six academic groups and two biotech companies have active Gramicidin S analog programs as of 2024. The GS14 series mentioned earlier has moved into preclinical toxicology. A separate program at the University of Manitoba (where much of the foundational analog work was done by Robert Hancock's group) is pursuing analogs with enhanced Gram-negative coverage by increasing the hydrophobic moment of the molecule.

Coating of medical devices. Surgical implants — orthopedic prostheses, catheters, stents — are prime sites for biofilm-associated infections that are nearly impossible to treat with systemic antibiotics. Gramicidin S, because of its stability and potency against biofilms, is being investigated as a surface coating. A 2023 paper in *Biomaterials* showed that titanium surfaces coated with Gramicidin S-loaded polymer films reduced *S. aureus* biofilm formation by >99% over 30 days in vitro without cytotoxicity to osteoblasts at the contact surface.

Inhalation delivery for lung infections. *Pseudomonas aeruginosa* lung infections in cystic fibrosis patients are a major unmet need. While Gramicidin S's Gram-negative activity is limited, GS analogs with improved Gram-negative coverage are being tested in nebulized formulations where systemic absorption is minimal and local concentrations can be high. The hemolytic concern is reduced in this context because alveolar epithelial cells have a different membrane composition than erythrocytes.

Combination immunotherapy approaches. The anti-inflammatory properties identified in some Gramicidin S analogs have sparked interest in formulations that simultaneously kill bacteria and dampen the excessive inflammatory response that drives tissue damage in severe infections. The specific questions being addressed: Do Gramicidin S analogs inhibit TLR4 signaling? Can they reduce NET (neutrophil extracellular trap) formation? What are the NF-κB inhibition kinetics?

Resistance mechanism mapping. Despite the theoretical resistance barrier, comprehensive genomic studies of clinical isolates exposed to Gramicidin S in Eastern European countries (where it has been used longest) are underway. The question: has 80 years of topical use in one healthcare system produced any detectable population-level resistance shifts? Preliminary metagenomic data from two Eastern European research groups (presented at ECCMID 2023) suggest the answer is no — resistance gene frequencies in Gramicidin S-using regions are indistinguishable from regions without use history. This is remarkable and, if confirmed, would be a powerful argument for Gramicidin S as a resistance-sparing antibiotic scaffold.

Antiviral applications. Emerging data suggest that the membrane-disrupting activity of Gramicidin S extends to enveloped viruses, which rely on a lipid envelope for cell entry. A 2022 preprint (not yet peer-reviewed) reported activity against SARS-CoV-2 pseudovirions at concentrations of 4–8 μg/mL in cell-free virucidal assays. This line of research is very early but conceptually interesting.

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Key Takeaways

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