Daptomycin is a cyclic lipopeptide antibiotic with potent bactericidal activity primarily against Gram-positive bacteria, including multidrug-resistant strains such as methicillin-resistant Staphylococcus aureus (MRSA) and vancomycin-resistant enterococci (VRE). It was discovered in the late 1980s from the fermentation broth of Streptomyces roseosporus. Its clinical significance stems from its unique mechanism of action, which differs from other classes of antibiotics, making it a valuable therapeutic agent for serious skin and soft tissue infections, as well as Staphylococcus aureus bacteremia and right-sided infective endocarditis.
The peptide consists of 13 amino acids, 10 of which are arranged in a cyclic structure, and a lipophilic tail (decanoic acid) attached to the N-terminal tryptophan residue. This structure is crucial for its mechanism, which involves calcium-dependent insertion into the bacterial cell membrane. Daptomycin was approved for clinical use by the U.S. Food and Drug Administration (FDA) in 2003, representing an important advancement in the antimicrobial arsenal against resistant Gram-positive pathogens.
Quick Facts
| Also Known As | Cubicin, LY146032 |
|---|---|
| Sequence | D-Ala-L-Asp-D-Asn-Gly-L-Asp-D-Ser-L-Gly-L-Orn-L-Asp-D-Ala-L-Asp-Gly-D-Ser-threo-3-methyl-L-Glu-L-Kyn-D-Asn-L-Thr-D-Gly-L-Orn-D-Asp-L-Thr-D-Ser-L-Glu-Orn-D-Ser-L-Thr-D-Ser-L-Orn-Hex-D-Orn-L-Thr-D-Ser-L-Orn-Gly-D-Ser-L-Thr-D-Asn-Lys |
| Molecular Formula | C72H101N17O26 |
| Molecular Weight | 1620.7 Da |
| PubChem CID | 21585658 |
Research Parameters
| Half-Life | Approximately 8-9 hours in healthy adults with normal renal function. |
|---|---|
| Stability | Lyophilized powder is stable when stored as recommended. After reconstitution with appropriate diluent (e.g., 0.9% Sodium Chloride Injection), the solution is stable for 12 hours at room temperature or up to 48 hours if refrigerated at 2-8°C. Commercially available solutions in vials are for single use only. |
| Solubility | Reconstituted with 0.9% Sodium Chloride Injection. Bacteriostatic Water for Injection is not recommended for initial reconstitution due to incompatibility. |
| Vial Size | 500 mg |
| Storage (Lyophilized) | Store unopened vials at 2-8°C (refrigerated). Protect from light. |
| Storage (Reconstituted) | Store reconstituted solution in the vial at 2-8°C for up to 48 hours. Do not freeze. Administer within 12 hours if stored at room temperature. |
| Typical Research Dose | Not applicable as a research peptide. Clinical doses are in mg/kg (e.g., 4-6 mg/kg). |
| Cycle Parameters | Not applicable. Administered as a daily intravenous infusion for a defined treatment course based on infection type and clinical response, typically 7 days to several weeks. |
| Amino Acid Count | 73 |
Mechanism of Action
Daptomycin exerts its bactericidal effect through a calcium-dependent, multi-step mechanism that disrupts the bacterial cell membrane function, leading to rapid cell death without lysis. Its action is concentration-dependent and requires the presence of physiological levels of calcium ions (Ca2+), which facilitate its oligomerization and insertion into the membrane.
Calcium-Dependent Oligomerization: In the presence of Ca2+, daptomycin undergoes a conformational change, forming oligomeric complexes on the surface of the bacterial cytoplasmic membrane. This binding is specific to membranes containing phosphatidylglycerol, a phospholipid abundant in Gram-positive bacteria.
Membrane Insertion and Depolarization: The oligomeric complexes insert into the cytoplasmic membrane, forming ion channels or pores that allow potassium efflux. This causes a rapid, concentration-dependent depolarization of the membrane potential. The loss of membrane potential disrupts critical cellular processes such as DNA, RNA, and protein synthesis.
Inhibition of Macromolecular Synthesis: Membrane depolarization leads to the cessation of macromolecular synthesis. Unlike beta-lactam antibiotics, daptomycin does not cause cell lysis; instead, bacterial death occurs without significant release of intracellular contents, potentially reducing inflammatory responses associated with infection.
Secondary Effects on Cell Wall Synthesis: While its primary target is the membrane, evidence suggests daptomycin may also interfere with cell wall biosynthesis by mislocalizing essential cell wall synthesis proteins, contributing to its bactericidal activity.
Research Applications
Antimicrobial Therapy Research: Daptomycin is a cornerstone in research investigating treatments for multidrug-resistant Gram-positive infections. Studies focus on its efficacy against MRSA, VRE, and other resistant pathogens in various infection models, including bacteremia, endocarditis, osteomyelitis, and prosthetic device infections. Research also explores its synergy with other antibiotics to enhance efficacy and prevent resistance.
Mechanism of Action and Resistance Studies: As a model lipopeptide, daptomycin is extensively used to study bacterial membrane biology, mechanisms of antibiotic resistance (e.g., alterations in membrane phospholipid composition, charge repulsion via mprF gene mutations), and the role of calcium in antimicrobial activity. This research is critical for developing next-generation lipopeptides.
Pharmacokinetic/Pharmacodynamic (PK/PD) Modeling: Research utilizes daptomycin to develop and validate PK/PD models that optimize dosing regimens for different patient populations (e.g., obese patients, those with renal impairment) and infection types, aiming to maximize efficacy while minimizing toxicity, such as creatine phosphokinase (CPK) elevation.
Biofilm Eradication Research: Investigations explore daptomycin's ability, often in combination with other agents, to penetrate and eradicate bacterial biofilms on medical implants and devices, a significant challenge in managing device-related infections.
Safety & Side Effects
The primary safety concern from clinical studies is skeletal muscle toxicity, manifesting as elevated creatine phosphokinase (CPK) levels, with rare cases of rhabdomyolysis. Patients are monitored weekly for CPK levels. Other reported adverse effects include gastrointestinal symptoms (nausea, diarrhea, vomiting), injection site reactions, headache, and insomnia. Hypersensitivity reactions, including anaphylaxis, are possible. Eosinophilic pneumonia is a rare but serious reported side effect. Theoretical concerns include the potential for peripheral neuropathy and the development of bacterial resistance during prolonged therapy. In animal toxicology studies, high doses have been associated with muscle and nerve damage.
Dosage Information
This information is derived from clinical and preclinical research studies and is presented for educational purposes only. Daptomycin is a prescription antibiotic, not a research peptide for human experimentation.
In approved human clinical use, daptomycin is administered intravenously. The typical dose for complicated skin and skin structure infections is 4 mg/kg once every 24 hours. For Staphylococcus aureus bacteremia and right-sided infective endocarditis, the dose is 6 mg/kg once every 24 hours. Dosing frequency is adjusted in patients with significant renal impairment (creatinine clearance <30 mL/min) to once every 48 hours. The duration of therapy typically ranges from 7 to 14 days for skin infections and 2 to 6 weeks or longer for bacteremia/endocarditis, depending on clinical response.
References
Steenbergen, J.N., Alder, J., Thorne, G.M., Tally, F.P. Daptomycin: a lipopeptide antibiotic for the treatment of serious Gram-positive infections. Journal of Antimicrobial Chemotherapy, 2005. 55(3): 283-288.
Carpenter, C.F., Chambers, H.F. Daptomycin: another novel agent for treating infections due to drug-resistant gram-positive pathogens. Clinical Infectious Diseases, 2004. 38(7): 994-1000.
Silverman, J.A., Perlmutter, N.G., Shapiro, H.M. Correlation of daptomycin bactericidal activity and membrane depolarization in Staphylococcus aureus. Antimicrobial Agents and Chemotherapy, 2003. 47(8): 2538-2544.
Fowler, V.G., Boucher, H.W., Corey, G.R., et al. Daptomycin versus standard therapy for bacteremia and endocarditis caused by Staphylococcus aureus. New England Journal of Medicine, 2006. 355(7): 653-665.
Jiang, J.H., Bhuiyan, M.S., Shen, H.H., et al. Genetic basis of daptomycin resistance in methicillin-resistant Staphylococcus aureus. mBio, 2019. 10(6): e01659-19.
Pogliano, J., Pogliano, N., Silverman, J.A. Daptomycin-mediated reorganization of membrane architecture causes mislocalization of essential cell division proteins. Journal of Bacteriology, 2012. 194(17): 4494-4504.
Bayer, A.S., Schneider, T., Sahl, H.G. Mechanisms of daptomycin resistance in Staphylococcus aureus: role of the cell membrane and cell wall. Annals of the New York Academy of Sciences, 2013. 1277: 139-158.