NVG-291

What is NVG-291?

NVG-291 is an investigational cell-penetrating peptide therapeutic in development by NervGen Pharma (Vancouver, TSX-V: NGEN / OTC: NRVGF) as a disease-modifying treatment for spinal cord injury and adjacent CNS injury indications. The active sequence is a 24-amino-acid synthetic peptide derived from the intracellular regulatory 'wedge' domain of protein tyrosine phosphatase sigma (PTPσ) — the receptor that, on the surface of CNS neurons, binds chondroitin sulfate proteoglycans (CSPGs) deposited in glial scar tissue and blocks axonal regeneration past the injury site. To get the cargo peptide into neurons, it is fused to the HIV-1 TAT cell-penetrating sequence (the same TAT-fusion approach used historically for delivering peptides across the plasma membrane). Once inside the cell, the wedge-domain peptide disrupts the CSPG-PTPσ signaling complex, releasing the inhibitory brake on axon growth and remyelination and allowing neuroplastic regrowth across the inhibitory scar. The molecule originated from Jerry Silver's laboratory at Case Western Reserve University, where the founding Nature 2015 paper (Lang et al.) established that ISP could produce remarkable functional recovery in rodent SCI models. NervGen Pharma was founded in 2017 to translate this work, advancing NVG-291 through Phase 1 healthy-volunteer safety into a Phase 1b/2a trial (NCT05965700) in chronic and subacute cervical spinal cord injury. The chronic cohort topline reported in June 2025 met statistical significance on one of two co-primary endpoints — a ~3-fold increase in motor evoked potential amplitude to the first dorsal interosseus hand muscle — with positive trends on the GRASSP hand-function score. NVG-291 is not approved for any indication and is available only through sponsored clinical trials.

What NVG-291 Is Investigated For

NVG-291 is one of the most-watched investigational peptides in the spinal cord injury / CNS neuroregeneration space, and the first compound in over a decade to produce a positive Phase 1b/2a readout on objective electrophysiological recovery in chronic SCI patients. The lead clinical indication is spinal cord injury, with NCT05965700 enrolling chronic (1–10 years post-injury) and subacute (within 1 year of injury) cervical SCI cohorts; the chronic cohort topline reported in June 2025 met statistical significance on motor evoked potential amplitude (~3-fold increase to the first dorsal interosseus hand muscle, an established corticospinal-tract integrity readout) and showed a positive trend on the GRASSP composite hand-function score. The subacute cohort is ongoing. FDA Fast Track designation has been granted. Beyond SCI, the same PTPσ-CSPG mechanism is preclinically relevant to multiple sclerosis (Dyck et al., Nat Commun 2018 — ISP enhanced MMP-2 activity and promoted recovery in EAE), ischemic stroke (Sami et al., Cell Rep 2022 — ISP promoted neuroblast migration, axonal sprouting, and functional recovery in mouse MCAO), preterm hypoxic-ischemic brain injury (Exp Neurol 2023), and Alzheimer's-related neurorepair narratives that NervGen has discussed publicly. The honest caveats are real: this is investigational, the Phase 1b/2a data is early and from a small cohort, only one of two co-primary endpoints reached statistical significance, and translating PTPσ-CSPG neurobiology from rodents to humans has been a notoriously difficult problem for the broader CNS-regeneration field. NVG-291 is not available outside sponsored trials, is not compoundable, and has no legitimate research-chemical or off-label use case. Read it as a high-conviction, mechanism-validated, mid-stage clinical asset — not a near-term consumer therapy.

History & Discovery

NVG-291's lineage runs through one of the most persistent investigators in the CNS-regeneration field. Jerry Silver, a developmental neurobiologist at Case Western Reserve University, spent decades characterizing the cellular and molecular machinery of the glial scar — the reactive astrocyte-driven tissue that forms after spinal cord and other CNS injury and that prevents axons from regenerating across the lesion. Through the 1990s and 2000s, Silver's laboratory and others (Geoff Raisman, Marie Filbin, Stephen Strittmatter, James Fawcett) collectively identified chondroitin sulfate proteoglycans (CSPGs) as the principal inhibitory matrix component of the glial scar, and chondroitinase ABC as an enzymatic tool capable of degrading CSPGs and unlocking regeneration in rodent models. The receptor-side discovery came in 2009, when Bret Shen and colleagues in the Silver laboratory reported in Science that PTPσ (protein tyrosine phosphatase sigma) was the long-sought neuronal receptor that binds CSPGs and transduces the inhibitory signal. This converted the glial scar from an inert physical barrier into a tractable pharmacology target: if the CSPG-PTPσ signaling axis could be blocked, the regenerative biology might be restored without enzymatically degrading the scar itself. The 2015 Nature paper (Lang, Cregg, et al.) was the conceptual breakthrough. The group designed a 24-residue synthetic peptide derived from PTPσ's intracellular regulatory wedge domain — exploiting the receptor's own autoinhibitory regulatory element — and fused it to the HIV-1 TAT cell-penetrating sequence to deliver the peptide into neurons. In rats with severe chronic thoracic spinal cord contusion injuries, daily subcutaneous TAT-ISP (intracellular sigma peptide) starting 6 weeks after injury produced striking functional recovery of locomotion and urinary continence, with serotonergic axon sprouting visible below the lesion on histology. The 6-week chronic-injury onset of treatment was particularly notable — prior interventions in SCI had largely required acute-phase administration, while chronic-phase recovery had been a stubbornly intractable problem. NervGen Pharma was founded in 2017 by Paul Brennan and others to translate the Silver-laboratory work clinically. The company licensed the intellectual property, advanced NVG-291 through GMP scale-up and IND-enabling toxicology, and initiated Phase 1 healthy-volunteer studies in 2020-2021 establishing safety and pharmacokinetic profiles across escalating subcutaneous doses. The Phase 1b/2a NCT05965700 trial in chronic (1-10 years post-injury) and subacute (within 1 year) cervical spinal cord injury opened enrollment in 2023. The chronic-cohort topline reported in June 2025 met one of two co-primary endpoints (3-fold MEP amplitude increase to the FDI hand muscle) and showed a positive GRASSP trend — the first such pharmacologic signal in chronic human SCI. FDA Fast Track designation followed, and the company has indicated it is consulting with FDA on Phase 2/3 design. NervGen's broader pipeline extends beyond NVG-291. A preclinical candidate, NVG-300, targets the same PTPσ axis with structural variations and is being positioned for stroke, ALS, and adjacent CNS injury indications. The broader CSPG-targeting field includes chondroitinase ABC variants (Acorda Therapeutics' historical work), Nogo-A antibody approaches (Schwab, ATI-3550), and other extrinsic-brake interventions. NVG-291's distinguishing claim is the peptide-pharmacology footprint (no need for viral delivery or enzymatic degradation of the scar) combined with the chronic-phase efficacy signal in both rodents and now humans.

How It Works

After a spinal cord injury, the body lays down scar tissue containing sugar-coated proteins called chondroitin sulfate proteoglycans (CSPGs) that act like a chemical wall — they bind to a receptor on nerve cells called PTPσ and signal 'do not grow.' That signal is one of the main reasons spinal cord injuries don't heal. NVG-291 is a small peptide that copies the natural off-switch inside the PTPσ receptor itself. Hooked to a delivery tag (HIV TAT), it gets into nerve cells and disrupts the CSPG-PTPσ signal, taking the brake off regeneration. In rodent spinal cord injury models, this allows axons to regrow across the scar. In the first human chronic-SCI trial, it tripled the electrical signal from the brain to a hand muscle.

NVG-291's mechanism is built on three connected discoveries from Jerry Silver's laboratory at Case Western Reserve University. First, in 2009 Shen et al. (Science) identified PTPσ as the long-sought neuronal receptor that binds chondroitin sulfate proteoglycans (CSPGs) in the glial scar and converts the structural lesion into an active inhibitory signal blocking axonal regeneration. Second, throughout the 2010s the group mapped the downstream signaling — PTPσ phosphatase activity dephosphorylates substrates including cortactin, autophagy regulators, and synaptic-organizing molecules, with the net effect of constraining axonal sprouting, oligodendrocyte progenitor differentiation, and remyelination at the injury site. Third, in the 2015 Nature paper (Lang et al.), the group designed a 24-residue peptide derived from PTPσ's intracellular regulatory wedge domain — the segment that normally serves as an autoinhibitory constraint on receptor function — and fused it to the HIV-1 TAT cell-penetrating sequence (TAT-ISP, or 'intracellular sigma peptide'). Delivered systemically, the TAT-ISP peptide crossed cell membranes, reached the intracellular face of PTPσ on neurons, and disrupted CSPG-induced PTPσ signaling. In rats with severe chronic contusion injuries of the thoracic spinal cord (treatment started 6 weeks post-injury, a chronic-injury setting that prior interventions had failed to address), 7 weeks of daily subcutaneous TAT-ISP produced striking recovery of locomotor function, urinary continence, and serotonergic axon sprouting below the lesion. NVG-291 is NervGen's clinical-grade version of this molecule (the rodent preclinical analog is denoted NVG-291-R). Pharmacology is consistent with the founding work: subcutaneous administration, peptide-class pharmacokinetics, intracellular delivery via TAT fusion, mechanism of action at intracellular PTPσ. Beyond CSPG-PTPσ disruption, ISP also engages autophagy-flux and lysosome-fusion pathways that support synaptic reorganization (Mol Neurobiol 2025), promotes a beneficial inflammatory response after SCI (Dyck et al., J Neuroinflammation 2018), enhances MMP-2 activity supporting matrix remodeling and recovery in EAE/MS models (Dyck et al., Nat Commun 2018), and promotes neuroblast migration and axonal sprouting after ischemic stroke (Sami et al., Cell Rep 2022). A 2025 Neurobiol Dis paper reported that PTPRS inhibition does not affect dopaminergic neuron survival or regeneration but does alter synaptic function in the nigrostriatal pathway — a finding that highlights the breadth of PTPσ's downstream synaptic roles and that the field should track for chronic-dosing safety. The Phase 1b/2a clinical readout (NCT05965700, chronic cohort topline June 2025) used motor evoked potential (MEP) amplitude to the first dorsal interosseus hand muscle as one of two co-primary endpoints. MEP amplitude is an established electrophysiological measure of corticospinal-tract integrity — the descending fiber tract whose damage is the principal cause of motor impairment in cervical SCI — and is a more direct functional biomarker than radiographic or biochemical surrogates. The reported roughly 3-fold MEP amplitude increase to the FDI hand muscle is the first such signal from a pharmacologic intervention in chronic human SCI and is consistent with the mechanism's prediction of restored corticospinal connectivity through CSPG-PTPσ disinhibition.

Evidence Snapshot

Research Gaps & Open Questions

What the current literature has not yet settled about NVG-291:

• 01Phase 2/3 confirmation — the Phase 1b/2a chronic-cohort topline met one of two co-primary endpoints in a small cohort; replication in a larger Phase 2/3 program with patient-reported and functional outcomes (independence with activities of daily living, work return, quality-of-life measures) is the critical next step.
• 02Subacute SCI cohort readout — whether NVG-291 produces equal, larger, or smaller effect in subacute (within 1 year) versus chronic (1-10 years) SCI is unresolved; mechanistic predictions favor a continuing benefit in both windows but the comparative data is forthcoming.
• 03Patient selection — which SCI patients respond best (level of injury, completeness of injury, time-since-injury, baseline corticospinal integrity, age, sex, comorbidities) is currently empirical and a major focus for late-phase development.
• 04Optimal dose and treatment duration — the Phase 1b/2a protocol used a defined treatment window; whether longer courses, repeat courses, or chronic dosing produce greater or durable recovery has not been characterized in humans.
• 05Translation to MS, stroke, and Alzheimer's — preclinical mechanism support exists across multiple CNS injury and neurodegeneration models, but no clinical efficacy signal exists yet in any indication beyond SCI.
• 06Long-term safety with repeated or chronic dosing — the 2025 dopaminergic-neuron synaptic-function paper is a reminder that PTPσ has broad synaptic roles and chronic-blockade safety will require careful surveillance.
• 07Comparison and combination with non-pharmacological approaches — epidural electrical stimulation, intensive locomotor training, and brain-computer interface-driven rehabilitation are advancing in parallel, and the optimal integration of NVG-291 with these approaches is unknown.

Forms & Administration

Subcutaneous injection, administered in a clinical trial setting under sponsor protocols. Dose ranges and frequency are trial-specific; published Phase 1 healthy-volunteer abstracts have used escalating doses approximately 0.1-0.75 mg/kg subcutaneously daily. NVG-291 is investigational and not available outside NervGen-sponsored clinical trials. There is no legitimate compounded, off-label, wellness, or research-chemical pathway, and any product marketed as NVG-291 outside the sponsor's trial supply chain is not the authentic clinical molecule. Patients interested in trial participation should consult ClinicalTrials.gov NCT05965700 and a spinal-cord-injury specialist.

Dosing & Protocols

The ranges below reflect protocols commonly discussed in the literature and by clinicians — not a prescription. Actual dosing for any individual should be determined by a qualified healthcare provider who knows the patient.

NVG-291 is an investigational drug in Phase 1b/2a clinical development by NervGen Pharma. It is not FDA-approved, not available outside sponsored clinical trials, not compoundable, and not authentic when sold through research-chemical or wellness channels. This entry is informational only and is not a prescription, dosing recommendation, or trial-recruitment endorsement.

Timeline of Effects

Common Questions

Who NVG-291 Is NOT For

Drug & Supplement Interactions

NVG-291 is a peptide therapeutic cleared by peptidase-mediated proteolysis and not by hepatic CYP-mediated metabolism, so classical small-molecule drug-interaction pathways are minimal in mechanistic terms. As an investigational drug, however, no comprehensive drug-interaction studies have been published; clinical-trial protocols restrict concomitant medications, particularly other investigational therapies, agents likely to confound electrophysiological measurements, and drugs with theoretical effects on neuronal repair or inflammation. Theoretical interactions worth flagging: chronic immunosuppressants (used in some SCI patients with autoimmune comorbidity) could modulate the beneficial inflammatory response that NVG-291 promotes through CSPG-PTPσ disruption (Dyck et al., J Neuroinflammation 2018). Concurrent investigational neuroregeneration therapies — chondroitinase ABC research products, Nogo-A antibodies, epidural electrical stimulation protocols — could plausibly combine additively or could complicate efficacy attribution; trial protocols generally exclude these. Standard SCI care (baclofen, gabapentin, tizanidine, pregabalin for spasticity and neuropathic pain; tamsulosin and intermittent catheterization for bladder; standard rehabilitation) is not expected to interact pharmacokinetically with NVG-291 and is generally continued during trial participation per protocol. Specific drug-interaction recommendations beyond trial protocols will emerge from later-phase development and eventual labeling.

Safety Profile

Legal Status

Regulatory status changes over time. Verify current local rules with a qualified professional.

Myths & Misconceptions