Background: DAB389IL-2 (Denileukin diftitox) as an immunotoxin is a targeted pharmaceutical
protein and is the first immunotoxin approved by FDA. It is used for the treatment of various
kinds of cancer such as CTCL lymphoma, melanoma, and Leukemia but among all of these, treatment
of CTCL has special importance. DAB389IL-2 consists of two distinct parts; the catalytic domain of
Diphtheria Toxin (DT) that genetically fused to the whole IL-2. Deamidation is the most important reaction
for chemical instability of proteins occurs during manufacture and storage. Deamidation of asparagine
residues occurs at a higher rate than glutamine residues. The structure of proteins, temperature
and pH are the most important factors that influence the rate of deamidation.
Methods: Since there is not any information about deamidation of DAB389IL-2, we studied in silico
deamidation by Molecular Dynamic (MD) simulations using GROMACS software. The 3D model of
fusion protein DAB389IL-2 was used as a template for deamidation. Then, the stability of deamidated
and native form of the drug was calculated.
Results: The results of MD simulations were showed that the deamidated form of DAB389IL-2 is more
unstable than the normal form. Also, deamidation was carried by incubating DAB389IL-2, 0.3 mg/ml in
ammonium hydrogen carbonate for 24 h at 37o C in order to in vitro experiment.
Conclusion: The results of in vitro experiment were confirmed outcomes of in silico study. In silico
and in vitro experiments were demonstrated that DAB389IL-2 is unstable in deamidated form.