Ostabolin-C
Also known as: Ostabolin C, PTH(1-31) cyclic lactam, RS-66271
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Summary
Ostabolin-C (also known as RS-66271) is a cyclic lactam analog of human parathyroid hormone fragment PTH(1-31), developed as a bone anabolic agent for osteoporosis. Its cyclization via a lactam bridge between Lys26 and Asp30 confers conformational stability and selective receptor signaling favoring bone formation over resorption. It was investigated as a potential alternative to teriparatide with improved safety profile, particularly regarding hypercalcemia.
Mechanism of Action
Selective PTH receptor (PTH1R) agonist; cyclic lactam analog of PTH(1-31) that stimulates osteoblast activity and bone formation while minimizing bone resorption signaling, promoting anabolic effects on bone with reduced hypercalcemic liability compared to full-length PTH.
Routes of Administration
Goals & Uses
- Osteoporosis treatmentBone MetabolismModerate
- Fracture risk reductionBone HealthLow
- Reduced hypercalcemia risk vs full PTHSafety ProfileModerate
- Increase bone mineral densityBone HealthModerate
Contraindications
- HypercalcemiaMetabolic DisorderHigh
- Severe renal impairmentOrganModerateKidney function concerns
- Paget's disease of boneBone DisorderModerate
- Prior radiation therapy to skeletonOncologic HistoryModerate
- Active malignancy or history of bone metastasesOncologicHigh
Adverse Effects
- Dizziness/orthostatic hypotensionCardiovascularUncommon
- HypercalcemiaMetabolicUncommon
- Injection site reactionsLocalCommon
- HypercalciuriaMetabolicUncommon
- NauseaGastrointestinalUncommonFeeling of sickness or urge to vomit
Drug Interactions
- BisphosphonatesLow
- DigoxinHigh
- Calcium supplementsModerate
- Vitamin D analogsModerate
Population Constraints
- Pediatric patientsAgeRelative
- Patients with hyperparathyroidismEndocrineAbsolute
- Pregnant womenReproductiveRelative
- Severe renal impairment (CrCl <30 mL/min)Organ ImpairmentRelative
Regulatory Status
- European UnionInvestigationalNo EMA marketing authorization obtained.
- United StatesInvestigationalNever received FDA approval; clinical development did not advance to NDA submission.
- United KingdomInvestigationalNo MHRA approval; remains a research compound.
Has not received regulatory approval in any major jurisdiction. Investigated primarily in preclinical and early clinical studies. Development was largely conducted by Allelix Biopharmaceuticals/NPS Pharmaceuticals in the 1990s–2000s.
Evidence & Sources
No sources recorded yet.
Frequently Asked Questions
What is Ostabolin-C?
Ostabolin-C (also known as RS-66271) is a cyclic lactam analog of human parathyroid hormone fragment PTH(1-31), developed as a bone anabolic agent for osteoporosis. Its cyclization via a lactam bridge between Lys26 and Asp30 confers conformational stability and selective receptor signaling favoring bone formation over resorption. It was investigated as a potential alternative to teriparatide with improved safety profile, particularly regarding hypercalcemia.
What is Ostabolin-C used for?
Ostabolin-C is educationally associated with: Osteoporosis treatment, Fracture risk reduction, Reduced hypercalcemia risk vs full PTH, Increase bone mineral density. Educational only — not medical advice.
How is Ostabolin-C administered?
Recorded routes of administration: Subcutaneous.
What are the potential side effects of Ostabolin-C?
Reported adverse effects include: Dizziness/orthostatic hypotension, Hypercalcemia, Injection site reactions, Hypercalciuria, Nausea. This list is not exhaustive — consult a qualified clinician.
Who should avoid Ostabolin-C?
Recorded contraindications: Hypercalcemia, Severe renal impairment, Paget's disease of bone, Prior radiation therapy to skeleton, Active malignancy or history of bone metastases. Consult a qualified clinician before use.