LTX-315

What is LTX-315?

LTX-315 is a first-in-class oncolytic peptide: a nine-amino-acid, cationic, amphipathic molecule that kills cells by physically disrupting their membranes rather than by binding a receptor or inhibiting an enzyme. It is given by direct intratumoral injection into lesions a clinician can reach, and it is investigational — not approved anywhere, for any indication. The molecule was designed rather than discovered. Lytix Biopharma, a spin-out from the University of Tromso in Norway, worked from the structural rules that make host-defence peptides lytic — a high net positive charge paired with bulky hydrophobic residues — and optimised that pharmacophore away from bacteria and toward cancer-cell membranes. The published lineage runs back to bovine lactoferrin and its antimicrobial fragment lactoferricin. The resulting molecule has the formula C78H106N18O9 and a molecular weight of about 1440 (PubChem CID 46200994). Its naming has become genuinely confusing. The compound now carries the international nonproprietary name ruxotemitide. Verrica Pharmaceuticals, which licensed it from Lytix in August 2020 for malignant and pre-malignant dermatological indications, develops it as VP-315, previously written VP-LTX-315. The original research literature, and most of the preclinical mechanism work, still calls it LTX-315. All four names refer to the same molecule. What makes it unusual among cancer drugs is that the cell death it causes is not selective in the conventional pharmacological sense — it is selective in that it is injected directly into the tumour and acts locally. The therapeutic hypothesis is not really about killing the injected tumour. It is that the particular way those cells die recruits an immune response capable of acting elsewhere in the body.

What LTX-315 Is Investigated For

LTX-315 has a clearer dermatological story than an oncological one, and the two are developing on different timelines. The dermatological programme is the furthest along. Verrica ran an open-label Phase 2 study in basal cell carcinoma (NCT05188729). In Part 2, 82 subjects with 92 tumours received 8 mg of VP-315 by intratumoral injection once daily for two to three consecutive days into up to two target lesions. The company reported 51 percent complete histologic clearance, an 86 percent overall reduction in tumour size, 71 percent reduction among tumours with residual carcinoma, and a 97 percent objective response rate — though that last figure is explicitly a post hoc analysis and should be read as such. No treatment-related serious adverse events were reported. Paired biopsies taken before treatment and at 12 to 14 weeks showed significant increases in CD3 positive, CD4 positive helper and CD8 positive cytotoxic T-cell densities, increased CD20 positive B-cell infiltration, and reduced immunosuppressive populations. These are company-reported conference data, presented at the Society for Immunotherapy of Cancer meeting in November 2025, and have not yet appeared as a peer-reviewed publication. The broader oncology programme is earlier and more sobering. The published Phase 1 dose-ranging trial (Spicer et al., Clinical Cancer Research 2021) treated 39 patients with advanced solid tumours. Substantial volume reduction of at least 30 percent occurred in 29 percent of injected lesions, and 12 of 14 post-treatment biopsies showed increased intralesional CD8 positive T cells — but there were no partial responses by immune-related response criteria, and grade 3 hypersensitivity or anaphylaxis occurred in 10 percent. A pilot combining LTX-315 with adoptive tumour-infiltrating lymphocyte therapy in metastatic soft tissue sarcoma enrolled six heavily pretreated patients, four of whom proceeded to cell therapy; the best response was stable disease for 208 days. The honest summary is that LTX-315 does what it is designed to do immunologically — it reliably converts injected tumours into T-cell-infiltrated ones, and expands T-cell clones detectable in blood — and that translating this into tumour responses has so far worked much better in a localised, accessible, immunogenic skin cancer than in advanced metastatic disease.

History & Discovery

LTX-315 came out of the antimicrobial peptide field rather than out of oncology, and that origin explains most of its properties. Through the 1990s, work on lactoferrin — an iron-binding protein in milk and mucosal secretions — established that its proteolytic fragment lactoferricin was directly antibacterial by membrane disruption. Researchers at the University of Tromso in northern Norway spent years dissecting which structural features of lactoferricin and related host-defence peptides were responsible for lysis, and arrived at a compact pharmacophore: a high net cationic charge paired with bulky hydrophobic residues, in a short sequence. The insight that turned this into a cancer programme was that the same pharmacophore distinguishes cancer-cell membranes from normal ones. Malignant cells expose more anionic lipid on their outer leaflet than healthy cells do, which gives a cationic lytic peptide a degree of preference even without any receptor. Lytix Biopharma was founded to exploit this, and iterated through a series of designed peptides — the LTX series — optimising for tumour-cell lysis rather than bacterial killing. LTX-315 emerged as the lead, with LTX-401 developed in parallel as a small-molecule analogue. The pivot that defined the programme came from the preclinical immunology. Early work showed intratumoral LTX-315 produced systemic, T-cell-mediated effects far out of proportion to the local tissue destruction — and in 2015 and 2016, a series of papers established why: the cell death was unregulated necrosis, and it carried every hallmark of immunogenic cell death. The drug was no longer a cytotoxic injected locally; it was an in situ vaccination strategy. Guido Kroemer's group in Paris, which had defined the immunogenic cell death framework in the first place, was closely involved in this characterisation. The first-in-human trial ran from 2013 to 2018 and was published in 2021. In August 2020, Verrica Pharmaceuticals licensed the molecule for dermatological oncology — explicitly excluding metastatic melanoma and metastatic Merkel cell carcinoma — and developed it as VP-315 in basal cell carcinoma, which is an unusually good fit: accessible lesions, high mutational burden, and a tumour type already known to respond to immune modulation. The World Health Organization later assigned the nonproprietary name ruxotemitide.

How It Works

Cancer-cell membranes carry more negative charge on their outer surface than healthy cell membranes do. LTX-315 is strongly positively charged, so it is drawn to them, inserts itself, and tears the membrane open — with a particular affinity for the membranes of mitochondria, the cell's power plants. The cell bursts rather than shutting down quietly, spilling its contents into the surrounding tissue. Those spilled contents are exactly the signals the immune system interprets as danger, so immune cells flood in, learn to recognise the tumour, and can then hunt the same cancer elsewhere in the body.

LTX-315 is a cationic amphipathic nonapeptide, and its mechanism follows from those two properties. The net positive charge drives preferential association with the anionic outer leaflet of cancer-cell plasma membranes, which carry more exposed phosphatidylserine and other negatively charged species than normal cells. The amphipathic arrangement then allows insertion into the lipid bilayer. Biophysical work with tumour model membranes has characterised this interaction directly. The critical target appears to be mitochondrial rather than plasma membrane. LTX-315 preferentially permeabilises mitochondrial membranes, producing a cell death that is partially regulated by BAX and BAK1 but is caspase-independent. The experimental evidence against apoptosis is unusually clean: no caspase-3 activation, no rescue by the pan-caspase inhibitor Z-VAD-fmk, no nuclear condensation on electron microscopy, and no rescue by necrostatin-1 or cyclosporin A, which exclude necroptosis and mitochondrial permeability transition as the mode of death. What remains is unregulated necrosis. That is the therapeutic mechanism, not a side effect of it. A necrotic cell spills its contents, and those contents are damage-associated molecular patterns. LTX-315 induces all four canonical hallmarks of immunogenic cell death — surface calreticulin exposure, extracellular ATP release, nuclear HMGB1 exodus and a type-1 interferon response — verified across biosensor cell lines by immunofluorescence, bioluminescence, immunoassay and RT-PCR. In vivo, intratumoral injection produces transiently haemorrhagic focal necrosis with HMGB1 released from close to all cancer cells. The immune consequences have been mapped in some detail. Released material drives MyD88-dependent maturation of dendritic cells, which prime T cells against antigens from the lysed tumour. Because the lysis is indiscriminate, the antigen pool includes private neoantigens specific to that patient's tumour — in the sarcoma pilot, T-cell reactivity against in silico predicted neoantigens was demonstrated in three of six patients, and de novo T-cell clones appeared and expanded in blood after injection. Work in Cell Stress showed the antitumor effect proceeds in two phases: an immediate lymphocyte-independent component, which is simply the direct lysis, followed by a lymphocyte-dependent component that accounts for durable and distant effects. A separate strand of mechanism concerns the checkpoint axis. In pancreatic cancer models, LTX-315 was found to downregulate PD-L1 by targeting ATP11B, a phospholipid flippase that maintains PD-L1 expression in a CMTM6-dependent manner; depleting ATP11B promotes lysosomal degradation of PD-L1. That provides a rationale for combining LTX-315 with checkpoint blockade that goes beyond simply adding two immune-stimulating agents, and preclinical work has shown synergy with anti-CTLA-4 antibodies in residual disease models.

Evidence Snapshot

Research Gaps & Open Questions

What the current literature has not yet settled about LTX-315:

• 01Does the basal cell carcinoma result hold up in a controlled trial? The 51 percent complete histologic clearance figure comes from an open-label, single-arm study with no comparator, and the 97 percent objective response rate is explicitly post hoc. Basal cell carcinoma has established treatments with high cure rates, so the relevant question is not whether VP-315 does something but whether it beats surgery, imiquimod or hedgehog inhibitors on outcomes patients care about, including cosmesis and recurrence.
• 02Why has the drug worked so much better in skin cancer than in advanced solid tumours? The Phase 1 trial produced no partial responses by immune-related criteria despite reliably producing necrosis and CD8 infiltration. Whether the difference is tumour type, disease burden, accessibility, prior treatment or the immunosuppressive environment of metastatic disease is unresolved, and it determines how broadly the approach can be applied.
• 03Is the abscopal effect real and reproducible? It has been reported in Phase 1 and suggested by histology in non-injected basal cell carcinoma lesions, but it has never been a prespecified endpoint in an adequately powered trial. Everything about the in situ vaccination rationale depends on it.
• 04What are the systemic pharmacokinetics after intratumoral injection? Lesion vascularity presumably governs how much drug escapes into the circulation, which would explain why hypotension and hypersensitivity vary, but this does not appear to have been characterised in published work.
• 05Does repeat dosing help or hurt? Every published protocol gives a single short course. Whether re-treating progressing lesions boosts the immune response, exhausts it, or provokes anti-drug reactions is unknown.
• 06Can responders be predicted? Neither baseline immune infiltration, tumour mutational burden, PD-L1 status nor any other candidate biomarker has been shown to predict who responds, which matters more for a therapy with a strictly local administration route than for a systemic one.
• 07The peptide has poor proteolytic stability and expensive synthesis — acknowledged problems that have driven several rounds of derivative design. Whether a stabilised analogue would retain the immunogenic cell death profile, or simply trade it for longer exposure, is unanswered.

Forms & Administration

LTX-315 is given exclusively by intratumoral injection, by a clinician, into lesions that can be reached directly or under imaging guidance. In the Phase 2 basal cell carcinoma programme, the dose was 8 mg in 0.5 mL injected once daily on two to three consecutive days, into up to two target lesions. There is no systemic, oral, topical or subcutaneous formulation, and no formulation intended for use outside a clinical trial. The injection itself is the therapeutic event. Because the drug acts by lysing cells it contacts, distribution within the lesion determines effect, and the technique — needle placement, fanning, volume per deposit — is part of the treatment rather than an administrative detail. Dose escalation in this class is limited less by systemic toxicity than by the volume a lesion can accept and by hypersensitivity reactions. LTX-315 is not available through any legitimate channel outside a trial. Material sold online under this name has no established identity, purity or sterility, and a peptide whose mechanism is indiscriminate membrane lysis is a genuinely dangerous thing to inject on that basis.

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.

LTX-315 is an investigational drug, not approved by any regulator for any indication, administered only by clinicians by direct intratumoral injection inside clinical trials. Material offered for sale under this name is not pharmaceutical-grade and has no verified identity or sterility. A peptide whose mechanism is indiscriminate membrane lysis causes necrosis wherever it is injected, and self-administration carries a realistic risk of tissue destruction and anaphylaxis.

Timeline of Effects

Common Questions

Who LTX-315 Is NOT For

Drug & Supplement Interactions

No formal drug interaction studies of LTX-315 have been published, and its pharmacokinetics after intratumoral injection are not well characterised in the public literature. As a short peptide it is expected to be degraded by ubiquitous peptidases rather than by cytochrome P450 enzymes, so classical metabolic interactions are unlikely — but this is an inference from chemistry rather than a measured finding. The interactions that are actually being studied are deliberate combinations. Checkpoint inhibitors are the main one: the ongoing clinical work pairs LTX-315 with pembrolizumab, and there is a specific mechanistic rationale beyond simple additivity, since preclinical work showed LTX-315 downregulates PD-L1 through the ATP11B and CMTM6 axis. Preclinical synergy with anti-CTLA-4 antibodies has also been reported in residual tumour models, as has combination with radiotherapy and with adoptive tumour-infiltrating lymphocyte therapy, the latter tested in a six-patient sarcoma pilot. The plausible negative interactions are pharmacological rather than pharmacokinetic. Systemic corticosteroids and other immunosuppressants would be expected to blunt the dendritic cell maturation and T-cell priming that constitute the therapeutic mechanism, leaving only the local lysis — the same concern that applies to checkpoint inhibitors generally. Antihistamines are relevant in the opposite direction, as premedication against the hypersensitivity and hypotension that cationic peptides can cause. Anticoagulants and antiplatelet agents deserve mention because the drug deliberately induces haemorrhagic necrosis in a tumour bed.

Safety Profile

Legal Status

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

Myths & Misconceptions