The invention relates to an insulin analogue or its pharmaceutically acceptable salt, pharmaceutical composition with prolonged therapeutic effect, application of the insulin analogue, dosage method and method of treatment of diabetes. In more detail, the solution pertains to compounds being stable insulin analogues which are pharmaceutically active and characterized by a prolonged, flat, truly peakless course of glucose concentration vs. time during repeated administration and which do not show strong 24 hours fluctuations of glucose concentration, or the so-called “sawteeth effect”, during this time. Results of studies of compounds included in the scope of this application indicate an improvement in the effects of diabetes treatment by avoiding the hitherto occurring adverse influence of changes in glucose concentration throughout the entire day on a patient's organism, e.g. night hypoglycaemias, because truly peakless, long-acting insulin should reproduce correct endogenous insulin secretion in the therapy, as is provided by a healthy pancreas at a proper and constant 24 hours level.