A Phase II Trial of RAB001 (LLP2A-Alendronate) for Steroid-Induced Early-Stage Osteonecrosis of the Femoral Head

Inclusion criteria

• 18 years ≤ age ≤ 69 years, gender not limited;
• Patients with glucocorticoid-induced osteonecrosis of the femoral head (ONFH) according to the 2019 edition of the "Guidelines for clinical diagnosis and treatment of osteonecrosis of the femoral head in adults", with an ARCO stage of II, and confirmed by CT and MRI examinations to have no femoral head collapse, and the time from first glucocorticoid use to the screening period must exceed 30 days;
• The participant has no plans for hip surgery on the target side within the next 54 weeks;
• Participants with unilateral or bilateral ONFH are not restricted. For unilateral involvement, the affected side (as the target side) must have no femoral head collapse confirmed by hip CT examination. For bilateral involvement, hip CT examination must confirm that at least one side has no collapse (the non-collapsed side is the target side; if both sides are necrotic and neither has collapsed, the side with more severe necrosis is the target side. If the contralateral side of the target side meets the criteria for study-defined osteonecrosis, all study information must be recorded for that side as for the target side);
• Participants must be informed about the study and voluntarily sign a written informed consent form before the trial.

Exclusion criteria

• BMI ≥ 35 kg/m²;
• The target-side osteonecrosis of the femoral head (ONFH) is classified as type M according to the China-Japan Friendship Hospital (CJFH) classification;
• Inability to walk or to complete all the examinations, treatments, and follow-ups required by the trial protocol;
• Currently receiving glucocorticoid pulse therapy;
• Severe metabolic diseases, cardiovascular diseases, clinically significant atrial fibrillation, uncontrolled hypertension, uncontrolled asthma, symptomatic pulmonary fibrosis, recent gastrointestinal bleeding requiring transfusion, mental or psychological disorders;
• History of deep vein thrombosis, with any invasive preventive/therapeutic measures taken within the last five years;
• Current fracture or infection in either hip joint, or previous surgery on the target-side hip joint;
• Planned oral surgery within 54 weeks after enrollment;
• Known hereditary bone diseases, such as achondroplasia, osteogenesis imperfecta, hypophosphatemic rickets, etc.;
• Use of medications for bone metabolic diseases, integrins, α4β1 inhibitors/antagonists, or anti-VEGF drugs within 6 months or 5 half-lives (whichever is longer) prior to screening, as detailed in section 12.7;
• Participants who have received opioid analgesics, non-steroidal anti-inflammatory drugs (NSAIDs), or other pain medications within 5 half-lives prior to screening;
• Comorbidities that, in the investigator's judgment, may affect the clinical efficacy assessment of the hip joint, such as knee osteoarthritis, scoliosis, pelvic or lower limb deformities, etc.;
• Previous allergy or contraindication to alendronate;
• Any of the following abnormal laboratory findings during screening:

Phosphate level < LLN; Patients with decompensated liver function (e.g., complications of portal hypertension such as ascites, gastroesophageal variceal bleeding, sepsis, hepatic encephalopathy, hepatorenal syndrome, etc.); Estimated glomerular filtration rate (eGFR) < 35 mL/min/1.73 m² (calculated based on creatinine using the CKD-EPI Creatinine 2009 Equation); Hemoglobin < 100 g/L; Prolonged QT interval (male > 450 msec, female > 470 msec).

• Donation or loss of blood/plasma > 400 mL within 3 months prior to screening (except for physiological blood loss in females);
• History of drug abuse within 2 years prior to screening;
• History of substance abuse within 2 years prior to screening;
• Pregnant or breastfeeding women, or female participants who have had unprotected sexual intercourse within 6 weeks prior to screening, or female participants with a positive blood pregnancy test; participants (or their partners) planning to conceive or donate sperm/eggs during the trial and for 6 months after study completion, or unwilling to use one or more contraceptive methods during the trial and for 6 months after study completion;
• Participation in other drug clinical trials with medication use within 3 months prior to screening;
• Participants deemed unsuitable for enrollment by the investigator.