Insulin lispro is a rapid-acting insulin analog developed to improve postprandial glycemic control in diabetes mellitus. It was the first insulin analog approved for clinical use, representing a significant milestone in diabetes therapy. Its development was driven by the need to mimic the physiological rapid rise and fall of endogenous insulin secretion in response to a meal, which conventional regular human insulin could not achieve due to its slower absorption profile.
Insulin lispro is a human insulin analog where the natural proline at position B28 and lysine at position B29 are reversed. This single amino acid substitution (ProB28Lys, LysB29Pro) reduces the propensity for self-association into dimers and hexamers, which are the rate-limiting steps for absorption of regular human insulin. This allows insulin lispro to be absorbed more rapidly from the subcutaneous injection site, leading to a faster onset and shorter duration of action. Its significance lies in providing a more physiological insulin replacement, reducing the risk of postprandial hyperglycemia and late post-injection hypoglycemia compared to regular human insulin.
Quick Facts
| Also Known As | Humalog, LY275585, Insulin analog lispro |
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| Sequence | Chain A: Gly-Ile-Val-Glu-Gln-Cys-Cys-Thr-Ser-Ile-Cys-Ser-Leu-Tyr-Gln-Leu-Glu-Asn-Tyr-Cys-Asn, Chain B: Phe-Val-Asn-Gln-His-Leu-Cys-Gly-Ser-His-Leu-Val-Glu-Ala-Leu-Tyr-Leu-Val-Cys-Gly-Glu-Arg-Gly-Phe-Phe-Tyr-Thr-Pro-Lys-Thr |
| Molecular Formula | C257H389N65O77S6 |
| Molecular Weight | 5814 Da |
| PubChem CID | 16132438 |
Research Parameters
| Half-Life | ~1 hour (subcutaneous). The terminal half-life after subcutaneous injection is approximately 1 hour, which is shorter than regular human insulin (~1.5 hours). |
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| Stability | Unopened, lyophilized (not typical) or liquid formulations are stable until the expiration date when stored refrigerated at 2-8°C. The commercial product (Humalog) is a solution, not lyophilized powder. Once in use (punctured vial or pen), stability is typically 28 days at room temperature (below 30°C/86°F) or refrigerated, as per manufacturer labeling. It should not be frozen. |
| Solubility | The commercial product is a ready-to-use sterile solution. For research-grade lyophilized material (if available), it is typically reconstituted with a provided diluent or sterile water for injection, often with a small amount of hydrochloric acid or sodium hydroxide to adjust pH. |
| Storage (Lyophilized) | For research-grade lyophilized material: Store at -20°C, protect from light and moisture. Stable for years under these conditions. |
| Storage (Reconstituted) | For a reconstituted research solution: Store at 2-8°C for short-term stability studies (often up to several weeks). Specific stability should be verified for the research formulation. Do not freeze. |
| Typical Research Dose | Dosing is almost exclusively in International Units (IU), not micrograms, due to its biological standardization. Research doses are highly variable but often range from 5-20 IU per injection (equivalent to roughly 175-700 mcg, using the approximate conversion of 1 IU = 35 mcg of insulin lispro). |
| Cycle Parameters | In clinical research for diabetes, it is used continuously as part of a basal-bolus regimen or in insulin pumps. There is no defined 'cycle' as with performance-enhancing peptides; administration is daily, typically as multiple subcutaneous injections (3 or more) timed with meals, for the duration of the study or treatment period. |
| Amino Acid Count | 50 |
Mechanism of Action
Insulin lispro functions identically to endogenous human insulin by binding to and activating the insulin receptor, a transmembrane tyrosine kinase receptor. This activation initiates a complex intracellular signaling cascade that regulates glucose, lipid, and protein metabolism, and influences cell growth and differentiation.
Primary Signaling Pathway (Metabolic): Upon binding to the alpha subunit of the insulin receptor, autophosphorylation of tyrosine residues on the intracellular beta subunit occurs. This activates the receptor's intrinsic tyrosine kinase activity, leading to the phosphorylation of insulin receptor substrates (IRS-1, IRS-2). Phosphorylated IRS proteins then recruit and activate phosphatidylinositol 3-kinase (PI3K), which generates phosphatidylinositol (3,4,5)-trisphosphate (PIP3). PIP3 activates protein kinase B (Akt/PKB), a central node that mediates most of insulin's metabolic actions. Akt activation stimulates the translocation of glucose transporter type 4 (GLUT4) vesicles to the cell membrane in muscle and adipose tissue, facilitating cellular glucose uptake. Akt also promotes glycogen synthesis (via inhibition of glycogen synthase kinase-3), protein synthesis (via mTOR activation), and inhibits gluconeogenesis and lipolysis.
Mitogenic Signaling Pathway: The activated insulin receptor also signals through the Ras/MAPK (mitogen-activated protein kinase) pathway, primarily via Shc and Grb2/SOS complex formation. This pathway is more associated with regulating gene expression, cell growth, and differentiation. While insulin lispro has the same receptor affinity as human insulin, its rapid pharmacokinetic profile may theoretically influence the temporal dynamics of these signaling pathways, though its mitogenic potency is considered equivalent to human insulin.
Research Applications
Diabetes Management Research: Insulin lispro is extensively studied as a model rapid-acting insulin in both type 1 and type 2 diabetes research. Its primary research benefit is in demonstrating the advantages of pharmacokinetic/pharmacodynamic (PK/PD) optimization. Studies consistently show it provides superior postprandial glucose control, reduced glycemic variability, and a lower risk of late hypoglycemia compared to regular human insulin, validating the analog design principle.
Closed-Loop Insulin Delivery Systems (Artificial Pancreas): Due to its rapid onset and predictable absorption, insulin lispro is a common insulin used in research on automated insulin delivery systems. Its pharmacokinetic profile is better suited for responding to meal announcements and correcting hyperglycemia in real-time within these algorithmic systems compared to slower insulins.
Pharmacoeconomic and Quality of Life Studies: Research has investigated the impact of insulin lispro on patient-reported outcomes, including treatment satisfaction, flexibility in meal timing, and reduction in fear of hypoglycemia. These studies contribute to understanding the broader value of rapid-acting analogs beyond pure glycemic metrics.
Safety & Side Effects
The safety profile of insulin lispro is well-characterized from decades of clinical use and is similar to other insulins, with hypoglycemia being the most common and serious adverse effect. In animal toxicology studies, the effects were consistent with excessive pharmacodynamic action (profound hypoglycemia).
Reported side effects from clinical trials include injection site reactions (pain, itching, redness), lipodystrophy with repeated use, allergic reactions (rare), and peripheral edema. Weight gain can occur with improved glycemic control. As with all insulin therapy, there is a risk of severe, life-threatening hypoglycemia, particularly if dosing is mismatched with food intake or physical activity.
Theoretical concerns historically included potential increased mitogenic potency due to structural changes, but extensive research has shown its binding affinity to the insulin-like growth factor-1 (IGF-1) receptor and mitogenic potential in vitro are not clinically significantly different from human insulin.
Dosage Information
DISCLAIMER: The following information is derived from published clinical and preclinical research studies and is presented for educational purposes only. It does not constitute medical advice.
In clinical research, insulin lispro is administered via subcutaneous injection, typically in the abdominal wall, thigh, or upper arm. The dose is highly individualized and based on body weight, carbohydrate intake, pre-meal blood glucose levels, and insulin sensitivity. In controlled studies, prandial doses often range from 0.05 to 0.2 units per kilogram of body weight per meal. It is usually injected immediately before (0-15 minutes) a meal, a key distinction from regular human insulin which requires injection 30-60 minutes prior. In continuous subcutaneous insulin infusion (insulin pump) research, it is used as the bolus insulin. Frequency is typically with each major meal (3 or more times daily). Duration of use in studies varies from acute single-dose PK/PD trials to long-term outcome studies lasting several years.
References
Howey, D.C., Bowsher, R.R., Brunelle, R.L., Woodworth, J.R. [Lys(B28), Pro(B29)]-human insulin: a rapidly absorbed analogue of human insulin. Diabetes. 1994;43(3):396-402.
Anderson, J.H. Jr, Brunelle, R.L., Koivisto, V.A., et al. Reduction of postprandial hyperglycemia and frequency of hypoglycemia in IDDM patients on insulin-analog treatment. Diabetes. 1997;46(2):265-70.
Home, P.D. The pharmacokinetics and pharmacodynamics of rapid-acting insulin analogues and their clinical consequences. Diabetes Obes Metab. 2012;14(9):780-8.
Bolli, G.B., Di Marchi, R.D., Park, G.D., Pramming, S., Koivisto, V.A. Insulin analogues and their potential in the management of diabetes mellitus. Diabetologia. 1999;42(10):1151-67.
Dunn, C.J., Plosker, G.L., Keating, G.M., McKeage, K., Scott, L.J. Insulin lispro: a review of its use in the management of diabetes mellitus. Drugs. 2003;63(4):407-35.
Heinemann, L., Woodworth, J.R., Bowsher, R.R., Brunelle, R.L. Pharmacokinetics of insulin lispro. Diabetologia. 1997;40 Suppl 2:S54-8.