CA-074 methyl ester

Summary

CA-074 methyl ester (CA‑074Me) is a research‑grade small‑molecule inhibitor of the cysteine protease cathepsin B. It is employed in cell‑culture and animal studies to probe the role of cathepsin B in processes such as ferroptosis, inflammasome activation, viral entry, and neurodegeneration. The compound is not an approved drug and is used experimentally via injection, oral dosing, or in‑vitro exposure.

Mechanism of Action

CA‑074Me is a selective, irreversible inhibitor of cathepsin B, a lysosomal cysteine protease. By covalently modifying the active‑site cysteine, it blocks proteolytic cleavage of substrates that drive lipid peroxidation, lysosomal membrane permeabilisation, and NLRP3 inflammasome assembly. In cell culture the ester is hydrolysed to the active acid, which can also form hydrogen bonds with the SARS‑CoV‑2 papain‑like protease (PLpro) BL2 groove, contributing to antiviral activity. Inhibition of cathepsin B therefore modulates ferroptotic cell death, pyroptosis, and inflammatory signaling.

What the Research Shows

Pre‑clinical work shows CA‑074Me reduces macrophage ferroptosis and improves functional recovery after spinal‑cord injury in mice (2023). In human iPSC‑derived cells, combined inhibition of TMPRSS2 and cathepsin B with CA‑074Me and camostat suppresses SARS‑CoV‑2 replication across multiple variants (2021). In APP/PS1 Alzheimer’s‑model mice, oral CA‑074Me, alone or with nimodipine, lowers NLRP3 inflammasome activation and improves memory performance (2025). Hepatic studies in high‑fat‑diet mice link CA‑074Me‑mediated cathepsin B inhibition to reduced pyroptosis. A bioluminescence assay identified intracellular hydrolysis of CA‑074Me as a source of PLpro inhibition. In a rat traumatic‑brain‑injury model, intracerebroventricular CA‑074Me altered cathepsin B localisation and reduced sensory hypersensitivity (2024). All findings are limited to animal or cell‑based systems.

Reported Benefits

Across the cited studies, CA‑074Me has demonstrated the ability to (1) limit ferroptotic damage in macrophages and support neurological recovery after spinal‑cord injury; (2) markedly lower SARS‑CoV‑2 viral load in iPSC models when paired with a TMPRSS2 inhibitor; (3) suppress NLRP3 inflammasome activity and improve learning‑memory outcomes in Alzheimer’s‑model mice; (4) attenuate hepatic pyroptosis in high‑fat‑diet mice; and (5) reduce post‑injury hypersensitivity in a rat traumatic‑brain‑injury model. These effects are consistently reported in pre‑clinical experiments.

Limitations of the Evidence

Evidence is confined to in‑vitro assays and animal models; no human clinical data exist. The compound’s pharmacokinetics, optimal dosing, and long‑term safety remain undefined. Effects appear model‑specific, and cathepsin B inhibition alone does not fully prevent membrane disruption in traumatic‑brain‑injury studies. The antiviral benefit requires co‑administration with a TMPRSS2 inhibitor, and PLpro inhibition depends on intracellular ester hydrolysis, which may vary across tissues. Consequently, translational relevance is uncertain.

Safety Considerations

The published abstracts do not report observable adverse events in the animal or cell studies, but safety assessments were not a primary focus. As a potent protease inhibitor, CA‑074Me could interfere with normal lysosomal functions and protein turnover, potentially leading to off‑target effects. Its use is restricted to controlled research settings; no toxicology or human safety data are available.

How It Is Administered

CA‑074Me is administered experimentally as a methyl‑ester prodrug. Reported routes include addition to cell‑culture medium, intraperitoneal or intravenous injection, oral gavage in mice, subcutaneous delivery, and intracerebroventricular infusion in rats. Formulations are typically dissolved in DMSO or aqueous buffers appropriate for the chosen route.

Routes of Administration

Goals & Uses

• Cathepsin B inhibitionTarget ValidationHigh
• Apoptosis and autophagy pathway researchCell Biology ResearchModerate
• Anti‑inflammatory researchPreclinicalModerate
• Cancer biology researchOncology ResearchModerate
• Neuroprotection researchNeuroscience ResearchModerate
• NLRP3 inflammasome suppressionInflammation ResearchModerate
• Cathepsin B inhibition (in vitro/in vivo research)Research Tool / Enzyme InhibitionHigh

Contraindications

• Human therapeutic useRegulatory/safetyHigh

Adverse Effects

• Cytotoxicity at high concentrationsIn Vitro ToxicityUncommon
• Off-target protease inhibitionPharmacologicalRare
• Unknown toxicitySystemicUnknown

Drug Interactions

No drug interactions recorded yet.

Population Constraints

• Not for human administrationGeneral PopulationAbsolute

Regulatory Status

• European UnionUnapprovedNot authorized for clinical use
• United StatesUnapprovedResearch chemical only
• United KingdomUnapprovedResearch reagent only; not reviewed by MHRA.

Not approved for human therapeutic use; employed only in preclinical and in‑vitro studies.

Evidence & Sources

• Identification of Cathepsin B as a Therapeutic Target for Ferroptosis of Macrophage after Spinal Cord Injury
  Journal ArticleLowXu J, et al.2023-01-01T00:00:00.000000Z
• Dual inhibition of TMPRSS2 and Cathepsin Bprevents SARS-CoV-2 infection in iPS cells
  Journal ArticleLowHashimoto R, et al.2021-01-01T00:00:00.000000Z
• CA-074 methyl ester, an inhibitor of cathepsin B, combined with the calcium channel blocker Nimodipine inhibits NLRP3 inflammasome activation and alleviates the lesions of Alzheimer's disease transgenic mice
  Journal ArticleLowMeng F, et al.2025-01-01T00:00:00.000000Z
• Apigenin Alleviated High-Fat-Diet-Induced Hepatic Pyroptosis by Mitophagy-ROS-CTSB-NLRP3 Pathway in Mice and AML12 Cells
  Journal ArticleLowMeng Z, et al.2023-01-01T00:00:00.000000Z
• In-cell bioluminescence resonance energy transfer (BRET)-based assay uncovers ceritinib and CA-074 as SARS-CoV-2 papain-like protease inhibitors
  Journal ArticleLowLi M, et al.2024-01-01T00:00:00.000000Z
• The Effects of Cathepsin B Inhibition in the Face of Diffuse Traumatic Brain Injury and Secondary Intracranial Pressure Elevation
  Journal ArticleLowHernandez M, et al.2024-01-01T00:00:00.000000Z

Frequently Asked Questions