What is a Cytotoxicity Assay?

Cytotoxicity assays are developed to analyze the ability of certain drug compounds to destroy the healthy cells of an organism. Cytotoxic compounds can lead to accidental cell death (referred to as necrosis) or programmed cell death (referred to as apoptosis). During the nonclinical and clinical research phases of drug discovery and development, cytotoxicity assays assess the safety profile of the drug candidate. The method proves valuable in identifying off-target effects of certain drug compounds on the human body.

For drug compounds developed for cancer treatment, cytotoxicity assays are critical in a variety of testing activity. Compounds that can hinder or stop cell proliferation make strong anti-cancer candidates.

Multiple cytotoxicity assays are used to assess different cell functions such as cell membrane permeability, enzyme activity, ATP production, cell adherence, nucleotide uptake, and co-enzyme production. Cytotoxicity assay should be selected based on the drug compound and with careful consideration of cellular function. The most effective method for assessment of cytotoxicity of the drug compound is evaluating cell membrane integrity. Cells having cytotoxic effects often show signs of compromised membrane integrity.

Role of Cytotoxicity Assay during Drug Discovery, Preclinical, and Clinical Phases

Every new drug candidate is continuously subjected to extensive tests for safety and efficacy before approval. Cytotoxicity testing is one way to test the safety of a drug on target and off-target cells in early stages of drug development. Toxicity testing for on- and off-target effects is necessary for safe drug administration.

In vitro assessments establish the toxicity of a drug compound in the human body. The permeability, metabolic stability, and interactions to membrane transporter systems are assessed in cell models relevant to the human body. A safety profile is achieved by combining cytotoxicity assay testing with in vivo tests of absorption, distribution, metabolism, and excretion.

Although cytotoxicity assays aim at finding toxicity of the drug compound or sample compound, it is unlikely to assess toxicity with a single test accurately. Multiple screening models are used for cell viability assessments in various human cell lines.

Cytotoxicity Assay Testing services offered by NorthEast BioLab

Cytotoxicity assays are utilized during drug development before toxicological testing is performed. Cytotoxicity assays are additionally used for controlling the quality of manufactured drug compounds.
There are quantitative and qualitative methods of cytotoxicity testing. The quantitative cytotoxicity assays used by NorthEast BioLab are Luciferase-ATP assay and MTT assay, and the qualitative assays used are MEM elution, the direct contact test, and the agar diffusion test.

Quantitative Assays

Luciferase-ATP Assay – Cell viability is an alternate readout for cytotoxicity. Luciferase is a commonly used enzyme that converts luciferin to oxyluciferin in the presence of ATP. ATP is found in viable cells and is proportional to the number of viable cells present. This assay is adaptable to high-throughput formats. It is also a sensitive readout of cytotoxicity in a variety of cells.

MTT Assay – The MTT cytotoxicity assay uses 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide dye, commonly referred to as MTT. MTT is a yellow-colored water-soluble compound which is split by mitochondrial succinate dehydrogenase, giving rise to the violet-colored formazan. The conversion of MTT to formazan only occurs in viable cells.

Qualitative Assays

Qualitative assays, such as the MEM elution assay, direct contact test, and agar diffusion test are used infrequently. In these assays, cells are exposed to a drug or compound, and cell deformity is assessed visually, on a predetermined scale.

Why Choose NorthEast BioLab for your Cytotoxicity Testing?

NorthEast BioLab uses cytotoxicity testing as a marker for biocompatibility of the drug compounds or selected drug candidates. We perform these cytotoxicity tests as per our documented SOPs to ensure adequate safety screening of various drug compounds.

When the cytotoxicity test result of a sample compound is unfavorable, or the toxicity of the compound is beyond an acceptable range, the drug candidate cannot proceed to the next stage of drug development. In this situation, our team of scientists conducts a toxicity risk assessment to determine the mechanism of toxicity and identify potential pathways to mitigate the toxic effects of the drug candidate.

NorthEast BioLab understands the importance of cytotoxicity testing. Our scientists follow FDA guidelines to decide whether to proceed with a compound safely. We partner with clients to ensure that your final drug product is safe for the human cells.