Webinar Q and A | Optimizing DMPK Strategy for Peptide Drugs

Peptide drugs are known for their high specificity, strong target affinity, and low risk of off-target effects. However, compared to small molecule drugs, they suffer from low oral bioavailability, poor plasma stability, and short circulation time. Optimizing these DMPK (Drug Metabolism and Pharmacokinetics) properties of peptides is crucial for their development.

On Nov 6, 2024, Mr. Jianping Sun from the DMPK Department of WuXi AppTec delivered a comprehensive webinar during the AAPS (American Association of Pharmaceutical Scientists) eTalk, which shares our strategies for tackling these DMPK challenges and accelerating peptide drug development. Specifically, this webinar explored essential strategies for optimizing the DMPK profiles of peptides, including the selection of appropriate in vitro matrices, tailored sample processing techniques, and leveraging WuXi AppTec DMPK's extensive experience and study platforms. This blog compiled some frequently asked questions regarding peptide DMPK studies.

Q1. What dosage is typically required to detect metabolites in DMPK studies?

A: Dosage requirements vary based on factors such as in vitro EC₅₀ values, plasma and tissue binding fraction, bioavailability and elimination rate, etc. For long-acting peptides with nano-molar EC₅₀ values, the initial dosage is typically less than 1 mg/kg. Using the LC-MS/MS method, the LLOQ (lower limit of quantitation) can range from pg/mL to ng/mL. Take semaglutide as an example, it has a 13 nM EC₅₀ value with dosages ranging from 0.01 mg/kg to 0.1 mg/kg in nonclinical PD and PK studies.

Q2. Why is LogD7.4 not used as a more accurate predictor of permeability for peptides that don't fit within Lipinski's Rule of Five, considering the limitations of LogP?

A: LogP tends to overestimate the lipophilicity of ionizable compounds such as peptides. Using LogD values at certain physiological pH levels, such as 5.5 for the intestinal tract or 7.4 for blood circulation, might be a more feasible way to screen compounds according to the Rule of 5. The average difference between LogP and LogD at physiological pH is about 2-3 log units. For cyclic peptides, the recommended lipophilicity range may still be higher than the Rule of 5 when using LogD at pH 7.4.

Q3. Is EPSA primarily used for permeability estimates due to high nonspecific binding in Caco-2 and MDCK assays?

A: EPSA, in conjunction with LogD or LogP, serves as a valuable tool for estimating oral permeability. Additionally, Caco-2 and MDR-1-MDCK II assays provide insights into transporter-related influx and efflux.

Q4. How do we study peptide structure and binding behavior in DMPK studies?

A: In DMPK, we typically use LC-MS/MS for the peptide quantitation in various in vitro and in vivo matrices. LC-HRMS is used for metabolite identification and structure elucidation.

Q5. What is your experience with peptide bioavailability in the oral cavity or under the tongue for orally disintegrating tablets?

A: We have conducted orally disintegrating tablets for oral cavity/under-the-tongue administration.  It is recommended to use blank tablets to assess the disintegration time in the mouth, and conducting a saliva stability study may also be beneficial.

Q6. Can similar approaches used in Taspoglutide, where Exendin molecules are complexed with serum albumin, be applied to enhance the oral bioavailability of small molecular weight peptide analogs and drugs?

A: Fatty acid chain modifications or albumin-binding peptides are often used to enhance the binding affinity to albumin, thereby increasing plasma stability and half-life. Regarding oral bioavailability, gastrointestinal stability, and permeability are also essential factors to consider and optimize. It typically needs a permeability enhancer to improve oral absorption.

Q7. What de-adsorption agents are commonly used to reduce nonspecific binding in bioanalysis?

A: Commonly used desorption agents include surfactants such as Tween-20 and Triton X-100; competitive sorbents like plasma, BSA, and peptide analogs; acid or basic additives such as formic acid, acetic acid, trifluoroacetic acid, phosphoric acid, ammonia, and ammonium bicarbonate; and cosolvents like DMSO, acetonitrile, and Invitrosol™ (protein solubilizer). Other desorption approaches include using low-adsorption consumables and minimizing the transfer times of samples.

For more details, please click here to watch the webinar recording. If you have any other questions, please feel free to talk to a WuXi AppTec DMPK expert or send an email to DMPK_Service@wuxiapptec.com.

Committed to accelerating drug discovery and development, we offer a full range of discovery screening, preclinical development, clinical drug metabolism, and pharmacokinetic (DMPK) platforms and services. With research facilities in the United States (New Jersey) and China (Shanghai, Suzhou, Nanjing, and Nantong), 1,000+ scientists, and over fifteen years of experience in Investigational New Drug (IND) application, our DMPK team at WuXi AppTec are serving 1,600+ global clients, and have successfully supported 1,500+ IND applications.