Antigenicity of MY-5116 was studied in the experimental animals and the following results were obtained. MY-5116 was shown to be non-immunogenic in rabbits, guinea pigs and mice when given alone as immunogen. Protein conjugate of MY-5116 induced antibody of hapten specific antibody when using guinea pigs and mice as immunizing species. However, MY-5116 was shown to be not capable of reaction with anti MY-5116-OVA antibodies. Guinea pigs had no skin contact sensitivity against MY-5116 examined by means of maximization test. In conclusion, MY-5116 lacks immunogenicity and eliciting antigenicity in this experimental conditions and this suggests that drug allergic response would either not occur or be minimal, if any, when MY-5116 is administered clinically.