Ribupatide: Molecular Structure

Molecular Structure and Properties#

Ribupatide (HRS9531/KAI-9531) is a peptide-based dual GLP-1/GIP receptor agonist. Detailed molecular structure information, including amino acid sequence, molecular weight, and molecular formula, has not been publicly disclosed by Hengrui Pharma or Kailera Therapeutics. This is typical for proprietary molecules in active clinical development.

Structural Classification#

Based on its dual GLP-1/GIP receptor agonist activity, ribupatide belongs to the same pharmacological class as tirzepatide (Mounjaro/Zepbound). Dual GLP-1/GIP agonists are typically designed either from a GIP sequence backbone (as with tirzepatide) or engineered as chimeric peptides combining elements of both GLP-1 and GIP to achieve balanced dual receptor activation.

Key structural features that can be inferred from the class:

• Peptide backbone: Modified from either GLP-1 or GIP native sequences with amino acid substitutions for protease resistance
• Half-life extension: Likely incorporates a lipid modification (fatty acid or fatty diacid) for albumin binding, supporting the once-weekly injectable dosing
• Dual receptor binding: Engineered to maintain potent agonist activity at both GLP-1R and GIPR

Dual Formulation Strategy#

A distinctive feature of ribupatide's development is the dual formulation approach:

Injectable Formulation#

The injectable formulation is administered once weekly via subcutaneous injection. This implies a half-life in the range of several days, consistent with fatty acid-modified peptides. The pharmacokinetic profile appears to support sustained receptor engagement throughout the weekly dosing interval.

Oral Formulation#

Ribupatide has also been successfully formulated as a once-daily oral tablet. Oral delivery of peptide therapeutics is inherently challenging due to proteolytic degradation in the GI tract and poor transcellular absorption. The specific oral delivery technology used for ribupatide has not been publicly disclosed.

In the Phase 2 oral trial, doses of 10 mg, 25 mg, and 50 mg were evaluated once daily, with the 25 mg and 50 mg doses both achieving 12.1% weight loss at 26 weeks.

Pharmacokinetics#

Specific pharmacokinetic parameters for ribupatide have not been fully published. Based on clinical trial designs and outcomes:

• Injectable: Once-weekly dosing suggests a half-life of several days, consistent with albumin-binding peptide technology
• Oral: Once-daily dosing with consistent weight loss suggests adequate daily exposure despite the inherent bioavailability limitations of oral peptide delivery
• No plateau observed: In both injectable and oral Phase 2 trials, weight loss continued without plateau at end of treatment, suggesting continued pharmacological effect

Comparison with Tirzepatide#

As both are dual GLP-1/GIP agonists, structural comparison with tirzepatide is relevant:

• Tirzepatide: 39-amino acid peptide based on GIP sequence backbone with C20 fatty diacid at Lys20, half-life approximately 5 days
• Ribupatide: Structure not disclosed, but once-weekly dosing suggests comparable half-life extension technology
• Both achieve dual receptor activation, but specific receptor potency ratios may differ

Related Reading#

• Ribupatide overview and research guide
• Peptides similar to Ribupatide
• Ribupatide research evidence