Clinical Pharmacology for Kimyrsa
Mechanism Of Action
Oritavancin is an antibacterial drug [see Microbiology].
Pharmacodynamics
The antimicrobial activity of oritavancin appears to correlate with the ratio of area under the concentration-time curve to minimal inhibitory concentration (AUC/MIC) based on animal models of infection. The AUC from time zero to 72 hours correlates with antimicrobial activity in both preclinical and clinical studies.
Exposure-response analyses from both preclinical and clinical studies support the treatment of clinically relevant gram-positive microorganisms (e.g. S. aureus and S. pyogenes) causative of ABSSSI with a single 1,200 mg dose of oritavancin.
Cardiac Electrophysiology
In a thorough QTc study of 135 healthy subjects at a dose 1.3 times the 1,200 mg recommended dose, oritavancin did not prolong the QTc interval to any clinically relevant extent.
Pharmacokinetics
The mean (±SD) pharmacokinetic parameters of oritavancin products (KIMYRSA and oritavancin) in patients with ABSSSI are presented in Table 3.
Table 3: Mean (±SD) Pharmacokinetic Parameters following a single 1,200 mg dose of KIMYRSA by intravenous infusion over 1 hour (N= 50) and Oritavancin by intravenous infusion over 3 hours (N=50) in Patients with ABSSSI
| Pharmacokinetic Parameter |
KIMYRSA (1 hour)
Mean (± SD) |
Oritavancin (3 hour)
Mean (± SD) |
| Cmax (μg/mL) |
148 (±43.0) |
112 (±34.5) |
| AUC0-72 (h•μg /mL) |
1460 (±511) |
1470 (±582) |
| Cmax, Maximum plasma concentration; AUC0-72, Area under the plasma concentration-time curve from time zero to 72 hours; SD, Standard deviation. |
Oritavancin exhibits linear pharmacokinetics at a dose up to 1,200 mg. The mean, populationpredicted oritavancin concentration-time profile displays a multi-exponential decline with a long terminal plasma half-life.
Distribution
Oritavancin is approximately 85% bound to human plasma proteins.
Based on population pharmacokinetic (PK) analysis, the population mean total volume of distribution is estimated to be approximately 87.6 L, indicating that oritavancin is extensively distributed into the tissues.
Exposures of oritavancin in skin blister fluid were approximately 20% of those in plasma (AUC0-24) after single 800 mg dose in healthy subjects.
Metabolism/Excretion
Non-clinical studies, including in vitro human liver microsome studies, indicated that oritavancin is not metabolized. No mass balance study has been conducted in humans. In humans, oritavancin is slowly excreted unchanged in feces and urine, with less than 1% and 5% of the dose recovered in feces and urine, respectively, after 2 weeks of collection.
Oritavancin has a terminal half-life of approximately 245 hours and a clearance of 0.445 L/h, based on population PK analyses.
Specific Populations
No dosage adjustments of KIMYRSA are required for patients with mild-to-moderate renal or mild-to-moderate hepatic impairment or other subpopulations, including age, gender, race, and weight.
Renal Impairment
The PK of oritavancin was examined in the Phase 3 ABSSSI trials in patients with normal renal function, CrCL ≥80 mL/min (n=238), mild renal impairment, CrCL 50-79 mL/min (n=48), and moderate renal impairment, CrCL 30-49 mL/min (n=11). Population PK analysis indicated that mild-to-moderate renal impairment had no clinically relevant effect on the exposure of oritavancin. No dedicated studies in dialysis patients have been conducted.
The solubilizer HPβCD is excreted in urine. Clearance of HPβCD may be reduced in patients with renal impairment. The clinical significance of this finding is unknown.
Dosage adjustment of KIMYRSA is not needed in patients with mild or moderate renal impairment. The PK of oritavancin in patients with severe renal impairment have not been evaluated.
Hepatic Impairment
The PK of oritavancin was evaluated in study of subjects with moderate hepatic impairment (Child-Pugh Class B) (n=20) and compared with healthy subjects (n=20) matched for gender, age, and weight. There were no relevant changes in PK of oritavancin in subjects with moderate hepatic impairment.
Dosage adjustment of KIMYRSA is not needed in patients with mild or moderate hepatic impairment. The PK of oritavancin in patients with severe hepatic insufficiency has not been studied.
Age, Gender, Weight And Race
Population PK analysis from the Phase 3 ABSSSI trials in patients indicated that gender, age, weight, and race had no clinically relevant effect on the exposure of oritavancin. No dosage adjustment of KIMYRSA is warranted in these subpopulations.
Drug Interactions
In vitro studies with human liver microsomes showed that oritavancin inhibited the activities of cytochrome P450 (CYP) enzymes 1A2, 2B6, 2D6, 2C9, 2C19, and 3A4. The observed inhibition of multiple CYP isoforms by oritavancin in vitro is likely to be reversible and noncompetitive. In vitro studies indicate that oritavancin is neither a substrate nor an inhibitor of the efflux transporter P-glycoprotein (P-gp).
Drugs That Inhibit Or Induce CYP450 Enzymes
A screening drug-drug interaction study was conducted in healthy volunteers (n=16) evaluating the concomitant administration of a single 1,200 mg dose of oritavancin with probe substrates for several CYP450 enzymes. The results showed that oritavancin is a weak inducer of CYP3A4 (a decrease of 18% in the mean AUC of midazolam) and CYP2D6 (decrease of 31% in the ratio of dextromethorphan to dextrorphan concentrations in the urine after administration of dextromethorphan). Oritavancin was also a weak inhibitor of CYP2C19 (increase of 15% in the ratio of omeprazole to 5-OH-omeprazole concentrations in the plasma after administration of omeprazole) and CYP2C9 (with an increase of 31% in the mean AUC of warfarin) [see WARNINGS AND PRECAUTIONS , and DRUG INTERACTIONS].
In the screening drug-drug interaction study, co-administration of oritavancin resulted in an increase of 18% in the ratio of 1-methylxanthine + 1 methylurate + 5-acetylamino-6- formylamino-3-methyluracil (1X + 1U + AFMU) to 1,7-dimethylurate (17U) concentrations in the urine after administration of caffeine (CYP1A2 probe substrate), and an increase of 16% in the ratio of AFMU to (1X +1U) concentrations in the urine after administration of caffeine (NAcetyltransferase- 2 probe substrate). Co-administration of oritavancin did not change the mean systemic exposure of caffeine metabolite (Xanthine oxidase probe substrate).
A study to assess the drug-drug interaction potential of a single 1,200 mg dose of oritavancin on the pharmacokinetics of S-warfarin following a single dose was conducted in 36 healthy subjects. S-warfarin PK was evaluated following a single dose of warfarin 25 mg given alone, or administered at the start, 24, or 72 hours after a single 1,200 mg oritavancin dose. The results showed no effect of oritavancin on S-warfarin Cmax or AUC.
Microbiology
KIMYRSA is a semi-synthetic, lipoglycopeptide antibacterial drug. KIMYRSA exerts a concentration-dependent bactericidal activity in vitro against S. aureus, S. pyogenes, and E. faecalis.
Mechanism Of Action
Oritavancin has three mechanisms of action: (i) inhibition of the transglycosylation (polymerization) step of cell wall biosynthesis by binding to the stem peptide of peptidoglycan precursors; (ii) inhibition of the transpeptidation (crosslinking) step of cell wall biosynthesis by binding to the peptide bridging segments of the cell wall; and (iii) disruption of bacterial membrane integrity, leading to depolarization, permeabilization, and cell death. These multiple mechanisms contribute to the concentration-dependent bactericidal activity of oritavancin.
Resistance
In serial passage studies, resistance to oritavancin was observed in isolates of S. aureus and E. faecalis. Resistance to oritavancin was not observed in clinical studies.
Interaction With Other Antimicrobial Agents
In in vitro studies, oritavancin exhibits synergistic bactericidal activity in combination with gentamicin, moxifloxacin or rifampicin against isolates of methicillin-susceptible S. aureus (MSSA), with gentamicin or linezolid against isolates of heterogeneous vancomycin-intermediate S. aureus (hVISA), VISA, and vancomycin-resistant S. aureus (VRSA), and with rifampin against isolates of VRSA. In vitro studies demonstrated no antagonism between oritavancin and gentamicin, moxifloxacin, linezolid or rifampin.
Antibacterial Activity
Oritavancin has been shown to be active against most isolates of the following microorganisms, both in vitro and in clinical infections [see INDICATIONS].
Gram-Positive Bacteria
Staphylococcus aureus (including methicillin-resistant isolates)
Streptococcus agalactiae
Streptococcus anginosus group (includes S. anginosus, S. intermedius, and S. constellatus)
Streptococcus dysgalactiae
Streptococcus pyogenes
Enterococcus faecalis (vancomycin-susceptible isolates only)
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 oritavancin against isolates of a similar organism group. However, the efficacy of oritavancin in treating clinical infections due to these bacteria has not been established in adequate and well-controlled clinical trials.
Gram-positive Bacteria
Enterococcus faecium (vancomycin-susceptible isolates only)
Susceptibility Testing Methods
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.
Immunogenicity
Positive indirect and direct antiglobulin tests (IAT/DAT) have been noted with the administration of KIMYRSA and oritavancin in studies with healthy subjects and patients with ABSSSI. The observed incidence of anti-drug antibodies is highly dependent on the sensitivity and specificity of the assay. Differences in assay methods preclude meaningful comparisons of the incidence of anti-drug antibodies in the studies described below with the incidence of antidrug antibodies in other studies, including those of KIMYRSA or other oritavancin products.
In a randomized, open-label, multi-center ABSSSI study, positive IAT/DAT were reported in 9.6% (5/52) of subjects who received ORBACTIV, another oritavancin product, and 2% (1/50) of subjects who received KIMYRSA. Oritavancin-dependent red blood cell (RBC) antibodies were detected when tested in the presence of drug for three subjects in the oritavancin group 14 days after dosing.
In a multiple-dose study with oritavancin in healthy volunteers, 90% (9/10) of subjects had a positive IAT 14 days after the second infusion.
In a healthy volunteer study, 66% (22/32) of subjects receiving KIMYRSA had a positive IAT 15 days after receiving dosing and one subject had a positive DAT at 8 days after dosing.
There were no reports of hemolysis in subjects who had positive IAT/DAT in any of the above referenced studies.
An in vitro study further evaluated 403 stored plasma samples from 12 healthy subjects and from 101 patients with ABSSSI from previously conducted clinical studies at multiple timepoints in healthy subjects and in patients with ABSSSI. In samples collected during the 15- and 8-day windows following single-dose treatment in healthy volunteers (Study MDCO-ORI-15-01) and in patients with ABSSSI (Study ML-ORI-201), respectively, low level (<8) direct agglutinating (IgM) anti-oritavancin antibodies were detected in 19 of 113 (17%) subjects. There was no identified clinically significant effect of anti-drug antibodies on pharmacokinetics, pharmacodynamics, safety, or effectiveness of single-dose oritavancin. No hematologic adverse events were reported for subjects with a positive titer.
There were no identified clinically significant effects of anti-drug antibodies on pharmacokinetics, pharmacodynamics, safety, or effectiveness of KIMYRSA over the treatment duration of 14 days.
Positive IAT may interfere with cross-matching before blood transfusion [see DRUG INTERACTIONS].
Clinical Studies
Acute Bacterial Skin And Skin Structure Infections (ABSSSI)
A total of 1987 adults with clinically documented ABSSSI suspected or proven to be due to Gram-positive pathogens were randomized into two identically designed, randomized, doubleblind, multi-center, multinational, non-inferiority trials (Trial 1 and Trial 2) comparing a single 1,200 mg intravenous dose of oritavancin to intravenous vancomycin (1 g or 15 mg/kg every 12 hours) for 7 to 10 days. The primary analysis population (modified intent to treat, mITT) included all randomized patients who received any study drug. Patients could receive concomitant aztreonam or metronidazole for suspected Gram-negative and anaerobic infection, respectively. Patient demographic and baseline characteristics were balanced between treatment groups. Approximately 64% of patients were Caucasian and 65% were males. The mean age was 45 years and the mean body mass index was 27 kg/m2. Across both trials, approximately 60% of patients were enrolled from the United States and 27% of patients from Asia. A history of diabetes was present in 14% of patients. The types of ABSSSI across both trials included cellulitis/erysipelas (40%), wound infection (29%), and major cutaneous abscesses (31%). Median infection area at baseline across both trials was 266.6 cm2. The primary endpoint in both trials was early clinical response (responder), defined as cessation of spread or reduction in size of baseline lesion, absence of fever, and no rescue antibacterial drug at 48 to 72 hours after initiation of therapy.
Table 4 provides the efficacy results for the primary endpoint in Trial 1 and Trial 2 in the primary analysis population.
Table 4: Clinical Response Rates in ABSSSI Trials using Responders1, 2 at 48-72 Hours after Initiation of Therapy
|
Oritavancin
n /N (%) |
Vancomycin
n /N (%) |
Difference (95% CI)3 |
| Trial 1 |
391/475 (82.3) |
378/479 (78.9) |
3.4 (-1.6, 8.4) |
| Trial 2 |
403/503 (80.1) |
416/502 (82.9) |
-2.7 (-7.5, 2.0) |
1 Cessation of spread or reduction in size of baseline lesion, absence of fever (<37.7°C) and no rescue antibacterial drug at 48 to 72 hours.
2 Patients who died at 48 to 72 hours, after initiation of therapy or who had increase in lesion size at 48 to 72 hours, after initiation of therapy or who used non-study antibacterial therapy during first 72 hours or who had an additional, unplanned, surgical procedure or who had missing measurements during the first 72 hours from initiation of study drug were classified as non-responders.
3 95% CI based on the Normal approximation to Binomial distribution. |
A key secondary endpoint in these two ABSSSI trials evaluated the percentage of patients achieving a 20% or greater reduction in lesion area from baseline at 48-72 hours after initiation of therapy. Table 5 summarizes the findings for this endpoint in the two ABSSSI trials.
Table 5: Clinical Response Rates1 in ABSSSI Trials using Reduction in Lesion Area of 20% or Greater at 48-72 Hours after Initiation of Therapy
|
Oritavancin
n /N (%) |
Vancomycin
n /N (%) |
Difference (95% CI)2 |
| Trial 1 |
413/475 (86.9) |
397/479 (82.9) |
4.1 (-0.5, 8.6) |
| Trial 2 |
432/503 (85.9) |
428/502 (85.3) |
0.6 (-3.7, 5.0) |
1Patients who died at 48 to 72 hours, after initiation of therapy or who had increase in lesion size at 48 to 72 hours, after initiation of therapy or who used non-study antibacterial therapy during first 72 hours or who had an additional, unplanned, surgical procedure or who had missing measurements during the first 72 hours from initiation of study drug were classified as non-responders.
2 95% CI based on the Normal approximation to Binomial distribution |
Another secondary efficacy endpoint in the two trials was investigator-assessed clinical success at post therapy evaluation at Day 14 to 24 (7 to 14 days from end of blinded therapy). A patient was categorized as a clinical success if the patient experienced a complete or nearly complete resolution of baseline signs and symptoms related to primary ABSSSI site (erythema, induration/edema, purulent drainage, fluctuance, pain, tenderness, local increase in heat/warmth) such that no further treatment with antibacterial drugs was needed.
Table 6 summarizes the findings for this endpoint in the mITT and clinically evaluable population in these two ABSSSI trials. Note that there are insufficient historical data to establish the magnitude of drug effect for antibacterial drugs compared with placebo at the post therapy visits. Therefore, comparisons of oritavancin to vancomycin based on clinical success rates at these visits cannot be utilized to establish non-inferiority conclusions.
Table 6: Clinical Success Rates1 in ABSSSI Trials at the Follow-Up Visit (7-14 days after end of therapy)
|
Oritavancin
n /N (%) |
Vancomycin
n /N (%) |
Difference (95% CI)2 |
| Trial 1 |
| mITT3 |
378/475 (79.6) |
383/479 (80.0) |
-0.4 (-5.5, 4.7) |
| CE3 |
362/394 (91.9) |
370/397 (93.2) |
-1.3 (-5.0,2.3) |
| Trial 2 |
| mITT3 |
416/503 (82.7) |
404/502 (80.5) |
2.2 (-2.6, 7.0) |
| CE3 |
398/427 (93.2) |
387/408 (94.9) |
-1.6 (-4.9,1.6) |
1 Clinical success was defined if the patient experienced a complete or nearly complete resolution of baseline signs and symptoms as described above.
2 95% CI based on the Normal approximation to Binomial distribution.
3 mITT population consisted of all randomized patients who received study drug; CE population consisted of all mITT patients who did not have violations of inclusion and exclusion criteria, completed treatment and had investigator assessment at the Follow-Up Visit. |
Outcomes By Baseline Pathogen
Table 7 shows outcomes in patients with an identified baseline pathogen in the microbiological Intent-to-Treat (microITT) population in a pooled analysis of Trial 1 and Trial 2. The outcomes shown in the table are clinical response rates at 48 to 72 hours and clinical success rates at follow-up study day 14 to 24.
Table 7: Outcomes by Baseline Pathogen (microITT)
|
At 48-72 hours |
Study day 14 to 24 |
| Early Clinical Responder1 |
≥ 20% reduction in lesion size2 |
Clinical Success3 |
| Pathogen4 |
Oritavancin
n/N (%) |
Vancomycin
n/N (%) |
Oritavancin
n/N (%) |
Vancomycin
n/N (%) |
Oritavancin
n/N (%) |
Vancomycin
n/N (%) |
| Staphylococcus aureus |
388/472 (82.2) |
395/473 (83.5) |
421/472 (89.2) |
407/473 (86.0) |
390/472 (82.6) |
398/473 (84.1) |
| Methicillinsusceptible |
222/268 (82.8) |
233/272 (85.7) |
231/268 (86.2) |
232/272 (85.3) |
220/268 (82.1) |
229/272 (84.2) |
| Methicillinresistant |
166/204 (81.4) |
162/201 (80.6) |
190/204 (93.1) |
175/201 (87.1) |
170/204 (83.3) |
169/201 (84.1) |
| Streptococcus pyogenes |
21/31 (67.7) |
23/32 (71.9) |
24/31 (77.4) |
24/32 (75.0) |
25/31 (80.6) |
23/32 (71.9) |
| Streptococcus agalactiae |
7/8 (87.5) |
12/12 (100.0) |
8/8 (100.0) |
12/12 (100.0) |
7/8 (87.5) |
11/12 (91.7) |
| Streptococcus dysgalactiae |
7/9 (77.8) |
6/6 (100.0) |
6/9 (66.7) |
5/6 (83.3) |
7/9 (77.8) |
3/6 (50.0) |
| Streptococcus anginosus group |
28/33 (84.8) |
40/45 (88.9) |
29/33 (87.9) |
42/45 (93.3) |
25/33 (75.8) |
38/45 (84.4) |
| Enterococcus faecalis |
11/13 (84.6) |
10/12 (83.3) |
10/13 (76.9) |
8/12 (66.7) |
8/13 (61.5) |
9/12 (75.0) |
1 Early clinical response defined as a composite of the cessation of spread or reduction in size of baseline lesion, absence of fever and no rescue antibacterial drug at 48-72 hours.
2 Patients achieving a 20% or greater reduction in lesion area from baseline at 48-72 hours after initiation of therapy.
3 Clinical success was defined if the patient experienced a complete or nearly complete resolution of baseline signs and symptoms as described above.
4 Baseline bacteremia in the oritavancin arm with relevant microorganisms causing ABSSSI included four subjects with MSSA and seven subjects with MRSA. Eight of these eleven subjects were responders at 48 to 72 hours after initiation of therapy |