Subcutaneous Pharmacokinetic Evaluation of Monomeric Insulin and Lyumjev in Adults With Type 1 Diabetes

Background and Rationale Current rapid-acting insulin formulations used in automated insulin delivery systems are limited by slow pharmacokinetics that prevent optimal meal coverage without pre-meal announcement. These insulins are predominantly composed of hexamers (94%) when stored, which must dissociate to monomers for biological activity. The presence of zinc ions and metacresol in commercial formulations promotes hexamer stability, contributing to slower onset and prolonged duration of action.

This study evaluates a two-pronged approach to improve insulin pharmacokinetics: (1) zinc removal through EDTA chelation, and (2) metacresol concentration reduction through dilution. Previous research has shown that these modifications can improve oligomer composition and potentially enhance insulin action speed and duration.

Study Design This is a randomized, crossover, single-dose, within-subject pilot study. Each participant serves as their own control, receiving all three insulin formulations in randomized order across three separate visits.

Target Enrollment: 10 participants

Key Inclusion Criteria

• Age 18-60 years
• Clinical diagnosis of type 1 diabetes
• Insulin pump therapy and continuous glucose monitor use for ≥3 months
• For females: not pregnant or trying to conceive
• Ability to provide informed consent and follow protocol requirements

Key Exclusion Criteria

• Diabetic ketoacidosis in past 3 months
• Severe hypoglycemia (seizure/loss of consciousness) in past 3 months
• Blood donation within 8 weeks
• Known clinically significant anemia
• Pregnancy or lactation
• Active infection
• Chronic kidney disease (GFR <60 mL/min/1.73m²)

Study Interventions

Three insulin formulations will be tested:

• Test Insulin #1: U-200 Humalog diluted 1:1 with sterile water, EDTA, and mannitol solution to achieve U-100 concentration
• Test Insulin #2: U-500 Humulin diluted 1:4 with sterile water, EDTA, and mannitol solution to achieve U-100 concentration
• Comparator: U-100 Lyumjev (commercially available, unmodified)

All formulations will be prepared by Stanford Healthcare Investigational Drug Services Pharmacy under aseptic conditions and used within 2 hours of preparation.

Study Procedures

• Pre-injection: Participants suspend insulin delivery 60 minutes before injection and consume a standardized mixed meal (Boost drink at 8.0 mL/kg body weight, providing 17.3 g carbohydrates per 100 mL).
• Injection: Subcutaneous injection of assigned insulin at 0.20 u/kg body weight.

Sample Collection:

• Frequent blood sampling (4 mL EDTA tubes) every 5 minutes for first 60 minutes, then every 15 minutes until 360 minutes.
• Real-time glucose monitoring using Contour Next One glucometer
• Early termination allowed if glucose increases after 240 minutes
• Maximum blood volume: 132 mL per visit (or 2.0 mL/kg if <66 kg)

Sample Processing:

Blood samples centrifuged immediately, plasma transferred to microcentrifuge tubes in triplicate, frozen on dry ice, and stored at -80°C until insulin ELISA analysis.

Primary Endpoints

Pharmacokinetic parameters for each insulin formulation:

• Time to maximum insulin concentration (Tmax)
• Maximum plasma insulin concentration (Cmax)
• Elimination half-life (T1/2)
• Area under the concentration-time curve (AUC)

Statistical Analysis Non-parametric methods will be used due to small sample size. The Wilcoxon signed-rank test will compare insulin formulations, with statistical significance set at p<0.05. Results will be presented as median and interquartile range for each parameter.

Safety Considerations The study is categorized as no greater than low risk.

Potential risks include:

• Standard blood draw complications (pain, bruising, bleeding)
• Hyperglycemia from mixed meal or hypoglycemia from insulin
• Transient local reactions at injection site from EDTA-containing formulations Glucose monitoring will be increased to every 5 minutes if levels fall below 70 mg/dL.

Follow-up Participants will be contacted 1-2 days after each visit to assess for unusual hypoglycemic or hyperglycemic episodes.

Future Research With participant consent, stored blood samples may be used for future approved research studies. Samples will be identified only by study ID number to maintain confidentiality.

Significance This study addresses a critical limitation in current diabetes management technology. Despite advances in automated insulin delivery systems, slow insulin pharmacokinetics leave even well-controlled patients spending 5+ hours daily outside target glucose range. If successful, these novel formulations could significantly improve glucose control and quality of life for people with type 1 diabetes using insulin pump therapy.

Study Contact Information:

Ryan Kingman, Clinical Research Coordinator Email: rkingman@stanford.edu Institution: Stanford University Office: 453 Quarry Road, Palo Alto, CA 94304

Principal Investigator:

Rayhan Lal, MD Stanford University

Study Location:

Stanford Clinical and Translational Research Unit 800 Welch Road, Palo Alto, CA

Regulatory Information:

IND Number: 169699 Funding Source: Other (Non-NIH)