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CC50/ IC50 Assay

Pharmaceutical safety is an essential factor in the development of every medicament. It is essential to establish that an investigational product has antiviral activity at concentrations that can be achieved in vivo without inducing toxic effects to cells. Furthermore, in a cell culture model, the apparent antiviral activity of an investigational product can be the result of host cell death after exposure to the product. Thus, it is crucial to determine the cytotoxic potential of the formulation on the cell line used in the antiviral assays.

50% cytotoxicity concentrations (CC50) is the concentration of test compounds required to reduce cell viability by 50%. Cytotoxicity of the test compounds is best determined concurrently with uninfected cells to obtain the 50% cytotoxic concentration (CC50) values. Cytotoxicity tests use a series of increasing concentrations of the antiviral product to determine what concentration results in the death of 50 percent of the host cells. This value is the median cellular cytotoxicity concentration and is identified by the 50% cytotoxic concentration (CC50). We recommend determining the 50% cytotoxic concentration (CC50) values in both stationary and dividing cells from multiple relevant human cell types and tissues to ascertain the potential for cell-cycle, species, or tissue-specific toxicities. In-vitro susceptibility of viruses to antiviral agents is typically measured as the inhibitory concentration 50% (IC50), which is the concentration of antiviral that lowers 50% of the virus-induced cytopathic effect (CPE) and the number of plaques formed. The relative effectiveness of the investigational product in inhibiting viral replication compared to inducing cell death is defined as the therapeutic or selectivity index (SI). This allows the calculation of the selectivity index (SI), which is defined as the ratio of the 50% cytotoxic concentration (CC50) to the inhibitory concentration of 50% (IC50).

Selectivity index: SI = CC50/IC50

It is desirable to have a high therapeutic index giving maximum antiviral activity with minimal cell toxicity. Compounds with a selectivity index (SI) values ≥ 10 are generally considered to be active in vitro. Occasionally there are compounds identified that have SI values below 10 that are effective in animal infection models. Thus, selectivity index (SI) values obtained in vitro serve as a guide in pursuing active compounds for further drug development. The higher the SI ratio, the theoretically more effective and safe a drug would be during in vivo treatment for a given viral infection. The ideal drug would be cytotoxic only at very high concentrations and have antiviral activity at low concentrations, yielding a high selectivity index (SI) value and eliminating the target virus at concentrations well below its cytotoxic concentration. The selectivity index of a compound is a widely accepted parameter used to express a compound’s in vitro efficacy in inhibiting virus replication.

Creative Diagnostics provides CC50 / IC50 Assay service with a high level of assay sensitivity and accuracy. CC50 and IC50 will be drawn using sigmoidal dose-response curves, and the selectivity index (SI) of each compound was evaluated by dividing the CC50 with the IC50. We have rich experience serving pharmaceutical, biotechnology, contract research, and academic scientists. We are happy to help you with all steps of your assay to provide you with the key information that can help move your studies forward.

Figure 1. IC50 and CC50 of Micafungin (Yi-Jung Hoa, et al. (2018)).

Our Features

  • High degree of accuracy and statistical data confidence.
  • Pre-determined standard procedures for its execution.
  • Provides quantitative information regarding specific dosages of drugs and their effects on cell lines.
  • High sensitivity and accuracy.

Our Capabilities

  • Dengue virus (DENV)
  • Influenza virus (IFV)
  • Ross River virus (RRV)
  • Semliki forest virus (SFV)
  • Sindbis virus (SINV)
  • Zika virus (ZIKA)

(Other viruses or microorganisms may be available on request)

We combine infection and analytical expertise to provide our clients with the most powerful portfolio of antiviral and antimicrobial in vitro testing services. Facing an increasing demand for new antiviral and antimicrobial compounds for the treatment of infectious diseases, Creative Diagnostics can test these compounds in vitro to determine their potential efficacy in vivo models.


  1. Yi-Jung Hoa, et al. Micafungin is a novel anti-viral agent of chikungunya virus through multiple mechanisms. Antiviral Research. (2018)159: 134 -142


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We Are Providing Our Clients Antiviral & Antibacterial Services

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Antiviral Services - Creative Diagnostics

Creative Diagnostics provides expertise in antiviral (or antibacterial) assays and cell-based antiviral (or antibacterial) compound screening to other biotechnology and pharmaceutical companies.

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