• Adverse Events frequency and degree [ Time Frame: 26 weeks (4+22 weeks) ]
  Hypoglycemic episodes (glucose level < 3.9 mmol/l) frequency Occurrence of local reactions at injection sites Occurrence allergic reactions
• HbA1c [ Time Frame: 26 weeks ]
  Change in HbA1c from baseline
• Fasting Plasma Glucose Level [ Time Frame: 26 weeks ]
  Change in fasting plasma glucose level from baseline
• Seven-Point Glucose Testing [ Time Frame: 26 weeks ]
  Change in seven-point glucose testing results from baseline
• Insulin Dose [ Time Frame: 26 weeks ]
  Change in total insulin dose per body weight (U/kg) from baseline
• Body Mass Index [ Time Frame: 26 weeks ]
  Change in BMI from baseline
• Treatment Satisfaction [ Time Frame: 26 weeks ]
  Change in overall treatment satisfaction (DTSQ score) from baseline

• Diabetes Mellitus, Type 2
• Diabetes Mellitus

• Drug: Humalog Mix25
  Subcutaneus injections Humalog® Mix 25 twice daily during 4 weeks of glucose-level based dose titration, 24 weeks of treatment with stable doses
• Drug: Insulin Lispro Biphasic 25
  Subcutaneus injections Insulin Lispro Biphasic 25 ("Geropharm") twice daily during 4 weeks of glucose-level based dose titration, 24 weeks of treatment with stable doses

• Active Comparator: Humalog® Mix 25
  Insulin Humalog® Mix 25 twice daily, individually glucose-level based administered doses +/- 1 or 2 OADs in stable doses, started before enrollement
  Intervention: Drug: Humalog Mix25
• Experimental: Insulin Lispro Biphasic 25
  Insulin Lispro Biphasic 25 twice daily, individually glucose-level based administered doses +/- 1 or 2 OADs in stable doses, started before enrollement
  Intervention: Drug: Insulin Lispro Biphasic 25

Inclusion Criteria:

• Signed written consent
• Clinical diagnosis of type 2 diabetes mellitus for at least 6 months prior to screening
• Glycosylated hemoglobin (HbA1c) level of 7.6 to 12.0 % at screening (both values inclusive)
• Body mass index (BMI) of 18.0 to 35 kg/m2 at screening (both values inclusive)
• Stable doses OADs for at least 3 months prior to treatment of experimental drug
• Female patients of childbearing potential who are willing to use two acceptable methods of contraception, (e.g., intra-uterine device plus condom, spermicidal gel plus condom, diaphragm plus condom, etc.), from the time of screening and for the duration of the trial, through trial completion

Exclusion Criteria:

• Acute inflammation disease for 3 weeks prior to screening
• Deviation of the laboratory results conducted during the screening:

Hemoglobin value < 9,0 g/dl; Hematocrit value < 30 %; ALT and AST value > 2 folds as high as maximal normal value; Serum bilirubin value > 1.5 folds as high as maximal normal value

• History of hematological disorders that can affect the reliability of HbA1c estimation (hemoglobinopathies, hemolytic anemia, etc.)
• Serious blood loss for 3 months prior to screening (blood donation, surgery procedure, etc.)
• Contraindication to the use of insulin Lispro Biphasic 25
• Insulin resistance over 1.5 U/kg insulin pro day
• Presence of insulin antibodies in the blood at the screening ˃10 U/ml
• Use of 3 or more oral antidiabetic drugs (OAD)
• Presence of severe diabetes complications
• History or presence of uncontrolled diabetes mellitus for 6 months prior to screening
• Deviation of vital signs, which can influence to results
• History of administration of glucocorticoids for 1 year prior to screening
• History of autoimmune disease, except controlled autoimmune thyroid disease
• Pregnant and breast-feeding women
• History of hypersensitivity to any of the active or inactive ingredients of the insulin/insulin analogue preparations used in the trial, OR history of significant allergic drug reactions
• Administration of any immunosuppressive drugs (Cyclosporinum, Methotrexatum)
• Incomplete recovery after surgery procedure