Adults

Administer the appropriate volume of the reconstituted Daptomycin for Injection (concentration of 50 mg/ mL) to adult patients intravenously either by injection over a two (2) minute period or by intravenous infusion over a thirty (30) minute period [see Dosage and Administration ( 2.2, 2.4, 2.7)] .

Pediatric use information is approved for Merck & Co., Inc.'s Cubicin (daptomycin for injection). However, due to Merck & Co., Inc.'s marketing exclusivity rights, this drug product is not labeled with that pediatric information.

Adult Patients:

No dosage adjustment is required in adult patients with creatinine clearance (CL CR) greater than or equal to 30 mL/min. The recommended dosage regimen for Daptomycin for Injection in adult patients with CL CR less than 30 mL/min, including adult patients on hemodialysis or continuous ambulatory peritoneal dialysis (CAPD), is 4 mg/kg (cSSSI) or 6 mg/kg ( S. aureus bloodstream infections) once every 48 hours ( Table 3). When possible, Daptomycin for Injection should be administered following the completion of hemodialysis on hemodialysis days [see Warnings and Precautions ( 5.2, 5.8), Use in Specific Populations ( 8.6), and Clinical Pharmacology ( 12.3)] .

Pediatric Patients:

The dosage regimen for Daptomycin for Injection in pediatric patients with renal impairment has not been established.

Reconstitution of Daptomycin for Injection Vial

Daptomycin for Injection is supplied in single-dose vials, each containing 350 mg daptomycin as a sterile, lyophilized powder. The contents of a Daptomycin for Injection vial should be reconstituted, using aseptic technique, to 50 mg/mL as follows:

1. To minimize foaming, AVOID vigorous agitation or shaking of the vial during or after reconstitution.
2. Remove the polypropylene flip-off cap from the Daptomycin for Injection vial to expose the central portion of the rubber stopper.
3. Wipe the top of the rubber stopper with an alcohol swab or other antiseptic solution and allow to dry. After cleaning, do not touch the rubber stopper or allow it to touch any other surface.
4. Slowly transfer 7 mL of 0.9% sodium chloride injection through the center of the rubber stopper into the Daptomycin for Injection vial, pointing the transfer needle toward the wall of the vial. It is recommended that a beveled sterile transfer needle that is 21 gauge or smaller in diameter, or a needleless device is used, pointing the transfer needle toward the wall of the vial.
5. Ensure that all of the Daptomycin for Injection powder is wetted by gently rotating the vial.
   1. Allow the wetted product to stand undisturbed for 10 minutes.
   2. Gently rotate or swirl the vial contents for a few minutes, as needed, to obtain a completely reconstituted solution.

Administration Instructions

Parenteral drug products should be inspected visually for particulate matter prior to administration.

Slowly remove reconstituted liquid (50 mg daptomycin/mL) from the vial using a beveled sterile needle that is 21 gauge or smaller in diameter. Administer as an intravenous injection or infusion as described below:

Adults

In-Use Storage Conditions for Daptomycin for Injection Once Reconstituted in Acceptable Intravenous Diluents

Stability studies have shown that the reconstituted solution is stable in the vial for 12 hours at room temperature and up to 48 hours if stored under refrigeration at 2 to 8°C (36 to 46°F).

The diluted solution is stable in the infusion bag for 12 hours at room temperature and 48 hours if stored under refrigeration. The combined storage time (reconstituted solution in vial and diluted solution in infusion bag) should not exceed 12 hours at room temperature or 48 hours under refrigeration.

Pediatric use information is approved for Merck & Co., Inc.'s Cubicin (daptomycin for injection). However, due to Merck & Co., Inc.'s marketing exclusivity rights, this drug product is not labeled with that pediatric information.

Clinical Trial Experience in Adult Patients

Clinical trials enrolled 1,864 adult patients treated with daptomycin for injection and 1,416 treated with comparator.

Complicated Skin and Skin Structure Infection Trials in Adults

In Phase 3 complicated skin and skin structure infection (cSSSI) trials in adult patients, daptomycin for injection was discontinued in 15/534 (2.8%) patients due to an adverse reaction, while comparator was discontinued in 17/558 (3.0%) patients.

The rates of the most common adverse reactions, organized by body system, observed in adult patients with cSSSI (receiving 4 mg/kg daptomycin for injection) are displayed in Table 6.

Drug-related adverse reactions (possibly or probably drug-related) that occurred in <1% of adult patients receiving daptomycin for injection in the cSSSI trials are as follows:

Body as a Whole: fatigue, weakness, rigors, flushing, hypersensitivity

Blood/Lymphatic System: leukocytosis, thrombocytopenia, thrombocytosis, eosinophilia, increased International Normalized Ratio (INR)

Cardiovascular System: supraventricular arrhythmia

Dermatologic System: eczema

Digestive System: abdominal distension, stomatitis, jaundice, increased serum lactate dehydrogenase

Metabolic/Nutritional System: hypomagnesemia, increased serum bicarbonate, electrolyte disturbance

Musculoskeletal System: myalgia, muscle cramps, muscle weakness, arthralgia

Nervous System: vertigo, mental status change, paresthesia

Special Senses: taste disturbance, eye irritation

S. aureus Bacteremia/Endocarditis Trial in Adults

In the S. aureus bacteremia/endocarditis trial involving adult patients, daptomycin for injection was discontinued in 20/120 (16.7%) patients due to an adverse reaction, while comparator was discontinued in 21/116 (18.1%) patients.

Serious Gram-negative infections (including bloodstream infections) were reported in 10/120 (8.3%) daptomycin for injection-treated patients and 0/115 comparator-treated patients. Comparator-treated patients received dual therapy that included initial gentamicin for 4 days. Infections were reported during treatment and during early and late follow-up. Gram-negative infections included cholangitis, alcoholic pancreatitis, sternal osteomyelitis/mediastinitis, bowel infarction, recurrent Crohn's disease, recurrent line sepsis, and recurrent urosepsis caused by a number of different Gram-negative bacteria.

The rates of the most common adverse reactions, organized by System Organ Class (SOC), observed in adult patients with S. aureus bacteremia/endocarditis (receiving 6 mg/kg daptomycin for injection) are displayed in Table 7.

The following reactions, not included above, were reported as possibly or probably drug-related in the daptomycin for injection-treated group:

Blood and Lymphatic System Disorders: eosinophilia, lymphadenopathy, thrombocythemia, thrombocytopenia

Cardiac Disorders: atrial fibrillation, atrial flutter, cardiac arrest

Ear and Labyrinth Disorders: tinnitus

Eye Disorders: vision blurred

Gastrointestinal Disorders: dry mouth, epigastric discomfort, gingival pain, hypoesthesia oral

Infections and Infestations: candidal infection NOS, vaginal candidiasis, fungemia, oral candidiasis, urinary tract infection fungal

Investigations: blood phosphorous increased, blood alkaline phosphatase increased, INR increased, liver function test abnormal, alanine aminotransferase increased, aspartate aminotransferase increased, prothrombin time prolonged

Metabolism and Nutrition Disorders: appetite decreased NOS

Musculoskeletal and Connective Tissue Disorders: myalgia

Nervous System Disorders: dyskinesia, paresthesia

Psychiatric Disorders: hallucination NOS

Renal and Urinary Disorders: proteinuria, renal impairment NOS

Skin and Subcutaneous Tissue Disorders: pruritus generalized, rash vesicular

Other Trials in Adults

In Phase 3 trials of community-acquired pneumonia (CAP) in adult patients, the death rate and rates of serious cardiorespiratory adverse events were higher in daptomycin for injection-treated patients than in comparator-treated patients. These differences were due to lack of therapeutic effectiveness of daptomycin for injection in the treatment of CAP in patients experiencing these adverse events [see Indications and Usage ( 1.4)] .

Laboratory Changes in Adults

Complicated Skin and Skin Structure Infection Trials in Adults

In Phase 3 cSSSI trials of adult patients receiving daptomycin for injection at a dose of 4 mg/kg, elevations in CPK were reported as clinical adverse events in 15/534 (2.8%) daptomycin for injection-treated patients, compared with 10/558 (1.8%) comparator-treated patients. Of the 534 patients treated with daptomycin for injection, 1 (0.2%) had symptoms of muscle pain or weakness associated with CPK elevations to greater than 4 times the upper limit of normal (ULN). The symptoms resolved within 3 days and CPK returned to normal within 7 to 10 days after treatment was discontinued [see Warnings and Precautions ( 5.2)] . Table 8 summarizes the CPK shifts from Baseline through End of Therapy in the cSSSI adult trials.

S. aureus Bacteremia/Endocarditis Trial in Adults

In the S. aureus bacteremia/endocarditis trial in adult patients, at a dose of 6 mg/kg, 11/120 (9.2%) daptomycin for injection-treated patients, including two patients with baseline CPK levels >500 U/L, had CPK elevations to levels >500 U/L, compared with 1/116 (0.9%) comparator-treated patients. Of the 11 daptomycin for injection-treated patients, 4 had prior or concomitant treatment with an HMGCoA reductase inhibitor. Three of these 11 daptomycin for injection-treated patients discontinued therapy due to CPK elevation, while the one comparator-treated patient did not discontinue therapy [see Warnings and Precautions ( 5.2)] .

Pediatric use information is approved for Merck & Co., Inc.'s Cubicin (daptomycin for injection). However, due to Merck & Co., Inc.'s marketing exclusivity rights, this drug product is not labeled with that pediatric information.

Risk Summary

Limited published data on use of daptomycin for injection in pregnant women are insufficient to inform a drug-associated risk for major birth defects and miscarriage. In animal reproduction studies performed in rats and rabbits daptomycin was administered intravenously during organogenesis at doses 2 and 4-times, respectively, the recommended 6 mg/kg human dose (on a body surface area basis). No evidence of adverse developmental outcomes was observed.

The background risk of major birth defects and miscarriage for the indicated population is unknown. All pregnancies have a background risk of birth defect, loss, or other adverse outcomes. In the U.S. general population, the estimated background risk of major birth defects and miscarriage in clinically recognized pregnancies is 2-4% and 15-20%, respectively.

Data

Risk Summary

Limited published data report that daptomycin is present in human milk at infant doses of 0.1% of the maternal dose [see Data] 2,3,4. There is no information on the effects of daptomycin on the breastfed infant or the effects of daptomycin on milk production. The developmental and health benefits of breastfeeding should be considered along with the mother's clinical need for Daptomycin for Injection and any potential adverse effects on the breastfed infant from Daptomycin for Injection or from the underlying maternal condition.

Daptomycin for injection Administered over a 30-Minute Period in Adults

The mean and standard deviation (SD) pharmacokinetic parameters of daptomycin at steady-state following intravenous (IV) administration of daptomycin for injection over a 30-minute period at 4 to 12 mg/kg q24h to healthy young adults are summarized in Table 11.

Daptomycin pharmacokinetics were generally linear and time-independent at daptomycin for injection doses of 4 to 12 mg/kg q24h administered by IV infusion over a 30-minute period for up to 14 days. Steady-state trough concentrations were achieved by the third daily dose. The mean (SD) steady-state trough concentrations attained following the administration of 4, 6, 8, 10, and 12 mg/kg q24h were 5.9 (1.6), 6.7 (1.6), 10.3 (5.5), 12.9 (2.9), and 13.7 (5.2) mcg/mL, respectively.

Daptomycin for injection Administered over a 2-Minute Period in Adults

Following IV administration of daptomycin for injection over a 2-minute period to healthy adult volunteers at doses of 4 mg/kg (N=8) and 6 mg/kg (N=12), the mean (SD) steady-state systemic exposure (AUC) values were 475 (71) and 701 (82) mcg•h/mL, respectively. Values for maximum plasma concentration (C max) at the end of the 2-minute period could not be determined adequately in this study. However, using pharmacokinetic parameters from 14 healthy adult volunteers who received a single dose of daptomycin for injection 6 mg/kg IV administered over a 30-minute period in a separate study, steady-state C max values were simulated for daptomycin for injection 4 and 6 mg/kg IV administered over a 2-minute period. The simulated mean (SD) steady-state C max values were 77.7 (8.1) and 116.6 (12.2) mcg/mL, respectively.

Distribution

Daptomycin is reversibly bound to human plasma proteins, primarily to serum albumin, in a concentration-independent manner. The overall mean binding ranges from 90 to 93%.

In clinical studies, mean serum protein binding in adult subjects with creatinine clearance (CL CR) ≥30 mL/min was comparable to that observed in healthy adult subjects with normal renal function. However, there was a trend toward decreasing serum protein binding among subjects with CL CR<30 mL/min (88%), including those receiving hemodialysis (86%) and continuous ambulatory peritoneal dialysis (CAPD) (84%). The protein binding of daptomycin in adult subjects with moderate hepatic impairment (Child-Pugh Class B) was similar to that in healthy adult subjects.

The volume of distribution at steady-state (V ss) of daptomycin in healthy adult subjects was approximately

0.1 L/kg and was independent of dose.

Metabolism

In in vitro studies, daptomycin was not metabolized by human liver microsomes.

In 5 healthy adults after infusion of radiolabeled 14C-daptomycin, the plasma total radioactivity was similar to the concentration determined by microbiological assay. Inactive metabolites were detected in urine, as determined by the difference between total radioactive concentrations and microbiologically active concentrations. In a separate study, no metabolites were observed in plasma on Day 1 following the administration of daptomycin for injection at 6 mg/kg to adult subjects. Minor amounts of three oxidative metabolites and one unidentified compound were detected in urine. The site of metabolism has not been identified.

Excretion

Daptomycin is excreted primarily by the kidneys. In a mass balance study of 5 healthy adult subjects using radiolabeled daptomycin, approximately 78% of the administered dose was recovered from urine based on total radioactivity (approximately 52% of the dose based on microbiologically active concentrations), and 5.7% of the administered dose was recovered from feces (collected for up to 9 days) based on total radioactivity.

Specific Populations

Drug-Drug Interactions

Mechanism of Action

Daptomycin binds to bacterial cell membranes and causes a rapid depolarization of membrane potential. This loss of membrane potential causes inhibition of DNA, RNA, and protein synthesis, which results in bacterial cell death.

Resistance

The mechanism(s) of daptomycin resistance is not fully understood. Currently, there are no known transferable elements that confer resistance to daptomycin.

Interactions with Other Antibacterials

In vitro studies have investigated daptomycin interactions with other antibacterials. Antagonism, as determined by kill curve studies, has not been observed. In vitro synergistic interactions of daptomycin with aminoglycosides, β-lactam antibacterials, and rifampin have been shown against some isolates of staphylococci (including some methicillin-resistant isolates) and enterococci (including some vancomycin-resistant isolates).

Complicated Skin and Skin Structure Infection (cSSSI) Trials in Adults

The emergence of daptomycin non-susceptible isolates occurred in 2 infected patients across the set of Phase 2 and pivotal Phase 3 clinical trials of cSSSI in adult patients. In one case, a non-susceptible S. aureus was isolated from a patient in a Phase 2 trial who received daptomycin for injection at less than the protocol-specified dose for the initial 5 days of therapy. In the second case, a non-susceptible Enterococcus faecalis was isolated from a patient with an infected chronic decubitus ulcer who was enrolled in a salvage trial.

S. aureus Bacteremia/Endocarditis and Other Post-Approval Trials in Adults

In subsequent clinical trials in adult patients, non-susceptible isolates were recovered. S. aureus was isolated from a patient in a compassionate-use trial and from 7 patients in the S. aureus bacteremia/ endocarditis trial [see Clinical Studies ( 14.2)] . An E. faecium was isolated from a patient in a vancomycin-resistant enterococci trial.

Antimicrobial Activity

Daptomycin has been shown to be active against most isolates of the following microorganisms both in vitro and in clinical infections [see Indications and Usage ( 1)] .

Gram-Positive Bacteria

Enterococcus faecalis (vancomycin-susceptible isolates only)

Staphylococcus aureus (including methicillin-resistant isolates)

Streptococcus agalactiae

Streptococcus dysgalactiae subsp. equisimilis

Streptococcus pyogenes

The following in vitro data are available, but their clinical significance is unknown. At least 90 percent of the following bacteria exhibit an in vitro minimum inhibitory concentration (MIC) less than or equal to the susceptible breakpoint for daptomycin against isolates of genus or organism group. However, the efficacy of daptomycin in treating clinical infections due to these bacteria has not been established in adequate and well-controlled clinical trials.

Gram-Positive Bacteria

Corynebacterium jeikeium

Enterococcus faecalis (vancomycin-resistant isolates)

Enterococcus faecium (including vancomycin-resistant isolates)

Staphylococcus epidermidis (including methicillin-resistant isolates)

Staphylococcus haemolyticus

Susceptibility Testing

For specific information regarding susceptibility test interpretive criteria and associated test methods and quality control standards recognized by FDA for this drug, please see: https://www.fda.gov/STIC.

Adult Animals

In animals, daptomycin administration has been associated with effects on skeletal muscle. However, there were no changes in cardiac or smooth muscle. Skeletal muscle effects were characterized by microscopic degenerative/regenerative changes and variable elevations in creatine phosphokinase (CPK). No fibrosis or rhabdomyolysis was evident in repeat-dose studies up to the highest doses tested in rats (150 mg/kg/day) and dogs (100 mg/kg/day). The degree of skeletal myopathy showed no increase when treatment was extended from 1 month to up to 6 months. Severity was dose-dependent. All muscle effects, including microscopic changes, were fully reversible within 30 days following the cessation of dosing.

In adult animals, effects on peripheral nerve (characterized by axonal degeneration and frequently accompanied by significant losses of patellar reflex, gag reflex, and pain perception) were observed at daptomycin doses higher than those associated with skeletal myopathy. Deficits the dogs' patellar reflexes were seen within 2 weeks after the start of treatment at 40 mg/kg/day (9 times the human C max at the 6 mg/kg/day dose), with some clinical improvement noted within 2 weeks after the cessation of dosing. However, at 75 mg/kg/day for 1 month, 7 of 8 dogs failed to regain full patellar reflex responses within a 3-month recovery period. In a separate study in dogs receiving doses of 75 and 100 mg/kg/day for 2 weeks, minimal residual histological changes were noted at 6 months after the cessation of dosing. However, recovery of peripheral nerve function was evident.

Tissue distribution studies in rats showed that daptomycin is retained in the kidney but appears to penetrate the blood-brain barrier only minimally following single and multiple doses.

Juvenile Animals

Target organs of daptomycin-related effects in 7-week-old juvenile dogs were skeletal muscle and nerve, the same target organs as in adult dogs. In juvenile dogs, nerve effects were noted at lower daptomycin blood concentrations than in adult dogs following 28 days of dosing. In contrast to adult dogs, juvenile dogs also showed evidence of effects in nerves of the spinal cord as well as peripheral nerves after 28 days of dosing. No nerve effects were noted in juvenile dogs following 14 days of dosing at doses up to 75 mg/kg/day.

Administration of daptomycin to 7-week-old juvenile dogs for 28 days at doses of 50 mg/kg/day produced minimal degenerative effects on the peripheral nerve and spinal cord in several animals, with no corresponding clinical signs. A dose of 150 mg/kg/day for 28 days produced minimal degeneration in the peripheral nerve and spinal cord as well as minimal to mild degeneration of the skeletal muscle in a majority of animals, accompanied by slight to severe muscle weakness evident in most dogs. Following a 28-day recovery phase, microscopic examination revealed recovery of the skeletal muscle and the ulnar nerve effects, but nerve degeneration in the sciatic nerve and spinal cord was still observed in all 150 mg/kg/day dogs.

Following once-daily administration of daptomycin to juvenile dogs for 28 days, microscopic effects in nerve tissue were noted at a C max value of 417 mcg/mL, which is approximately 3-fold less than the C max value associated with nerve effects in adult dogs treated once daily with daptomycin for 28 days (1308 mcg/mL).

Neonatal Animals

Neonatal dogs (4 to 31 days old) were more sensitive to daptomycin-related adverse nervous system and/or muscular system effects than either juvenile or adult dogs. In neonatal dogs, adverse nervous system and/or muscular system effects were associated with a C max value approximately 3-fold less than the C max in juvenile dogs, and 9-fold less than the C max in adult dogs following 28 days of dosing. At a dose of 25 mg/kg/day with associated C max and AUC inf values of 147 mcg/mL and 717 mcg ·h/mL, respectively (1.6 and 1.0-fold the adult human C max and AUC, respectively, at the 6 mg/kg/day dose), mild clinical signs of twitching and one incidence of muscle rigidity were observed with no corresponding effect on body weight. These effects were found to be reversible within 28 days after treatment had stopped.

At higher dose levels of 50 and 75 mg/kg/day with associated C max and AUC inf values of ≥321 mcg/mL and ≥1470 mcg ·h/mL, respectively, marked clinical signs of twitching, muscle rigidity in the limbs, and impaired use of limbs were observed. Resulting decreases in body weights and overall body condition at doses ≥50 mg/kg/day necessitated early discontinuation by PND19.

Histopathological assessment did not reveal any daptomycin-related changes in the peripheral and central nervous system tissue, as well as in the skeletal muscle or other tissues assessed, at any dose level.

No adverse effects were observed in the dogs that received daptomycin at 10 mg/kg/day, the NOAEL, with associated C max and AUC inf values of 62 mcg/mL and 247 mcg ·h/mL, respectively (or 0.6 and 0.4-fold the adult human C max and AUC, respectively at the 6 mg/kg dose).

Adults with cSSSI

Adult patients with clinically documented complicated skin and skin structure infections (cSSSI) ( Table 17) were enrolled in two randomized, multinational, multicenter, investigator-blinded trials comparing daptomycin for injection (4 mg/kg IV q24h) with either vancomycin (1 g IV q12h) or an anti-staphylococcal semi-synthetic penicillin (i.e., nafcillin, oxacillin, cloxacillin, or flucloxacillin; 4 to 12 IV per day). Patients could switch to oral therapy after a minimum of 4 days of IV treatment if clinical improvement was demonstrated. Patients known to have bacteremia at baseline were excluded. Patients with creatinine clearance (CL CR) between 30 and 70 mL/min were to receive a lower dose of daptomycin for injection as specified in the protocol; however, the majority of the patients in this subpopulation did not have the dose of daptomycin for injection adjusted.

One trial was conducted primarily in the United States and South Africa (study 9801), and the second was conducted at non-US sites only (study 9901). The two trials were similar in design but differed in patient characteristics, including history of diabetes and peripheral vascular disease. There were a total of 534 adult patients treated with daptomycin for injection and 558 treated with comparator in the two trials. The majority (89.7%) of patients received IV medication exclusively.

The efficacy endpoints in both trials were the clinical success rates in the intent-to-treat-(ITT) population and in the clinically evaluable (CE) population. In study 9801, clinical success rates in the ITT population were 62.5% (165/264) in patients treated with daptomycin for injection and 60.9% (162/266) in patients treated with comparator drugs. Clinical success rates in the CE population were 76.0% (158/208) in patients treated with daptomycin for injection and 76.7% (158/206) in patients treated with comparator drugs. In study 9901, clinical success rates in the ITT population were 80.4% (217/270) in patients treated with daptomycin for injection and 80.5% (235/292) in patients treated with comparator drugs. Clinical success rates in the CE population were 89.9% (214/238) in patients treated with daptomycin for injection and 90.4% (226/250) in patients treated with comparator drugs.

The success rates by pathogen for microbiologically evaluable patients are presented in Table 18.

Pediatric use information is approved for Merck & Co., Inc.'s Cubicin (daptomycin for injection). However, due to Merck & Co., Inc.'s marketing exclusivity rights, this drug product is not labeled with that pediatric information.

Adults with S. aureus Bacteremia/Endocarditis

The efficacy of daptomycin for injection in the treatment of adult patients S. aureus bacteremia was demonstrated in a randomized, controlled, multinational, multicenter, open-label trial. In this trial, adult patients with at least one positive blood culture for S. aureus obtained within 2 calendar days prior to the first dose of study drug and irrespective of source were enrolled and randomized to either daptomycin for injection (6 mg/kg IV q24h) or standard of care [an anti-staphylococcal semi-synthetic penicillin 2 g IV q4h (nafcillin, oxacillin, cloxacillin, or flucloxacillin) or vancomycin 1 g IV q12h, each with initial gentamicin 1 mg/kg IV every 8 hours for first 4 days]. Of the patients in the comparator group, 93% received initial gentamicin for a median of 4 days, compared with 1 patient (<1%) in the daptomycin for injection group. Patients with prosthetic heart valves, intravascular foreign material that was not planned for removal within 4 days after the first dose of study medication, severe neutropenia, known osteomyelitis, polymicrobial bloodstream infections, creatinine clearance <30 mL/min, and pneumonia were excluded.

Upon entry, patients were classified for likelihood of endocarditis using the modified Duke criteria (Possible, Definite, or Not Endocarditis). Echocardiography, including a transesophageal echocardiogram (TEE), was performed within 5 days following study enrollment. The choice of comparator agent was based on the oxacillin susceptibility of the S. aureus isolate. The duration of study treatment was based on the investigator's clinical diagnosis. Final diagnoses and outcome assessments at Test of Cure (6 weeks after the last treatment dose) were made by a treatment-blinded Adjudication Committee, using protocol-specified clinical definitions and a composite primary efficacy endpoint (clinical and microbiological) success at the Test of Cure visit.

A total of 246 patients ≥18 years of age (124 daptomycin for injection, 122 comparator) with S. aureus bacteremia were randomized from 48 centers in the US and Europe. In the ITT population, 120 patients received daptomycin for injection and 115 received comparator (62 received an anti-staphylococcal semi-synthetic penicillin and 53 received vancomycin). Thirty-five patients treated with an anti-staphylococcal semi-synthetic penicillin received vancomycin initially for 1 to 3 days, pending final susceptibility results for the S. aureus isolates. The median age among the 235 patients in the ITT population was 53 years (range: 21 to 91 years); 30/120 (25%) in the daptomycin for injection group and 37/115 (32%) in the comparator group were ≥65 years of age. Of the 235 ITT patients, there were 141 (60%) males and 156 (66%) Caucasians across the two treatment groups. In addition, 176 (75%) of the ITT population had systemic inflammatory response syndrome (SIRS) at baseline and 85 (36%) had surgical procedures within 30 days prior to onset of the S. aureus bacteremia. Eighty-nine patients (38%) had bacteremia caused by methicillin-resistant S. aureus (MRSA). Entry diagnosis was based on the modified Duke criteria and comprised 37 (16%) Definite, 144 (61%) Possible, and 54 (23%) Not Endocarditis. Of the 37 patients with an entry diagnosis of Definite Endocarditis, all (100%) had a final diagnosis of infective endocarditis, and of the 144 patients with an entry diagnosis of Possible Endocarditis, 15 (10%) had a final diagnosis of infective endocarditis as assessed by the Adjudication Committee. Of the 54 patients with an entry diagnosis of Not Endocarditis, 1 (2%) had a final diagnosis of infective endocarditis as assessed by the Adjudication Committee.

In the ITT population, there were 182 patients with bacteremia and 53 patients with infective endocarditis as assessed by the Adjudication Committee, including 35 with right-sided endocarditis and 18 with left-sided endocarditis. The 182 patients with bacteremia comprised 121 with complicated S. aureus bacteremia and 61 with uncomplicated S. aureus bacteremia.

Complicated bacteremia was defined as S. aureus isolated from blood cultures obtained on at least 2 different calendar days, and/or metastatic foci of infection (deep tissue involvement), and classification of the patient as not having endocarditis according to the modified Duke criteria. Uncomplicated bacteremia was defined as S. aureus isolated from blood culture(s) obtained on a single calendar day, no metastatic foci of infection, no infection of prosthetic material, and classification of the patient as not having endocarditis according to the modified Duke criteria. The definition of right-sided infective endocarditis (RIE) used in the clinical trial was Definite or Possible Endocarditis according to the modified Duke criteria and no echocardiographic evidence of predisposing pathology or active involvement of either the mitral or aortic valve. Complicated RIE comprised patients who were not intravenous drug users, had a positive blood culture for MRSA, serum creatinine ≥2.5 mg/dL, or evidence of extrapulmonary sites of infection. Patients who were intravenous drug users, had a positive blood culture for methicillin-susceptible S. aureus (MSSA), had serum creatinine <2.5 mg/dL, and were without evidence of extrapulmonary sites of infection were considered to have uncomplicated RIE.

The coprimary efficacy endpoints in the trial were the Adjudication Committee success rates at the Test of Cure visit (6 weeks after the last treatment dose) in the ITT and Per Protocol (PP) populations. The overall Adjudication Committee success rates in the ITT population were 44.2% (53/120) in patients treated with daptomycin for injection and 41.7% (48/115) in patients treated with comparator (difference = 2.4% [95% CI −10.2, 15.1]). The success rates in the PP population were 54.4% (43/79) in patients treated with daptomycin for injection and 53.3% (32/60) in patients treated with comparator (difference = 1.1% [95% CI −15.6, 17.8]).

Adjudication Committee success rates are shown in Table 19.

Eighteen (18/120) patients in the daptomycin for injection arm and 19/116 patients in the comparator arm died during the trial. These comprise 3/28 daptomycin for injection-treated patients and 8/26 comparator-treated patients with endocarditis, as well as 15/92 daptomycin for injection-treated patients and 11/90 comparator-treated patients with bacteremia. Among patients with persisting or relapsing S. aureus infections, 8/19 daptomycin for injection-treated patients and 7/11 comparator-treated patients died.

Overall, there was no difference in time to clearance of S. aureus bacteremia between daptomycin for injection and comparator. The median time to clearance in patients with MSSA was 4 days and in patients with MRSA was 8 days.

Failure of treatment due to persisting or relapsing S. aureus infections was assessed by the Adjudication Committee in 19/120 (16%) daptomycin for injection-treated patients (12 with MRSA and 7 with MSSA) and 11/115 (10%) comparator-treated patients (9 with MRSA treated with vancomycin and 2 with MSSA treated with an anti-staphylococcal semi-synthetic penicillin). Among all failures, isolates from 6 daptomycin for injection-treated patients and 1 vancomycin-treated patient developed increasing MICs (reduced susceptibility) by central laboratory testing during or following therapy. Most patients who failed due to persisting or relapsing S. aureus infection had deep-seated infection and did not receive necessary surgical intervention [see Warnings and Precautions ( 5.7)] .

Pediatric use information is approved for Merck & Co., Inc.'s Cubicin (daptomycin for injection). However, due to Merck & Co., Inc.'s marketing exclusivity rights, this drug product is not labeled with that pediatric information.