Praziquantel is a synthesized pyrazine isoquinoline derivative, also called cyclo-praziquantel, and a white or off-white crystalline powder and bitter in taste. It is worldwide recognized as a highly effective and broad-spectrum anti-parasite drug and widely used for treating diseases such as schistosomiasis japonica, schistosomiasis haematobium, schistosomiasis mansoni, clonorchiasis, paragonimiasis, sparganosis mansoni, fasciolopsis, echinococcosis, taeniasis, cysticercosis, etc. It has advantages such as broad anti-parasitic spectrum, high efficacy, low toxicity, short therapeutic course and easy to use, etc. In addition to human use, it is also widely used in anti-parasitic treatment of animals including poultry and livestock. The invention of praziquantel is a major breakthrough in the history of anti-parasitic chemotherapy. In the past 30 years, praziquantel has still been the first choice of drug for treating various parasitic diseases on the market.
Praziquantel is a racemic compound composed of (R)-praziquantel and (S)-praziquantel together. Scientists have separated and obtained both pure optic isomers of (R)-praziquantel and (S)-praziquantel from synthesized praziquantel, and found in preclinical studies and preliminary clinical trials that: (R)-praziquantel is the active parasiticidal component of praziquantel, while the (S)-praziquantel is inactive or even harmful; at the same dosage, the clinical efficacy of (R)-praziquantel is better than that of praziquantel, and (S)-praziquantel has little activity, bitter taste and is the major source of drug side effects; (R)-praziquantel shows lower cardiac toxicity than (S)-praziquantel. Therefore, the development of (R)-praziquantel has clinical application values of higher efficacy, less side effects, and better medical compliance.
Chinese invention patent publication number CN102786520A discloses a Form A of praziquantel and a preparation method and application thereof. The reported praziquantel Form A shows that the Height %=100 peak is at the position where 2-Theta=20.0±0.2° or d=4.4±0.2 Å and 43 diffraction peaks exist when analyzed by powder X-ray diffraction.
Chinese invention patent publication number CN102786519A discloses a state of matter of Form B praziquantel, wherein the Height %=100 peak is at the position where 2-Theta=18.7±0.2° or d=4.7±0.2 Å in powder X-ray diffraction analysis.