Fidaxomicin

Fidaxomicin tablets are a macrolide antibacterial indicated in adult patients for the treatment of C. difficile -associated diarrhea. ( 1.1 ) To reduce the development of drug-resistant bacteria and maintain the effectiveness of fidaxomicin tablets and other antibacterial drugs, fidaxomicin tablets should be used only to treat infections that are proven or strongly suspected to be caused by C. difficile . ( 1.2 )

1.1 Clostridioides difficile -Associated Diarrhea Fidaxomicin tablets are indicated in adult patients for the treatment of C. difficile – associated diarrhea (CDAD).

1.2 Usage To reduce the development of drug-resistant bacteria and maintain the effectiveness of fidaxomicin tablets and other antibacterial drugs, fidaxomicin tablets should be used only to treat infections that are proven or strongly suspected to be caused by C. difficile . When culture and susceptibility information are available, they should be considered in selecting or modifying antibacterial therapy. In the absence of such data, local epidemiology and susceptibility patterns may contribute to the empiric selection of therapy. Pediatric use information is approved for Cubist Pharmaceuticals LLC's DIFICID ® (fidaxomicin) tablets. However, due to Cubist Pharmaceuticals LLC's marketing exclusivity rights, this drug product is not labeled with that information.

Fidaxomicin tablets 200 mg white to off-white film-coated, oblong tablets; each tablet is debossed with "200" on one side and plain on the other side. Film-coated tablets: 200 mg ( 3 )

Fidaxomicin tablets are contraindicated in patients who have known hypersensitivity to fidaxomicin or any other ingredient in fidaxomicin tablets [see Warnings and Precautions ( 5.1 )] . Fidaxomicin tablets are contraindicated in patients who have known hypersensitivity to fidaxomicin or any other ingredient in fidaxomicin tablets. ( 4 )

• Acute hypersensitivity reactions (angioedema, dyspnea, pruritus, and rash) have been reported. If a severe hypersensitivity reaction occurs, discontinue fidaxomicin tablets. ( 5.1 )
• Fidaxomicin tablets are not expected to be effective for the treatment of other types of infections due to minimal systemic absorption of fidaxomicin. Fidaxomicin tablets should only be used for the treatment of C. difficile-associated diarrhea. ( 5.2 )
• Development of drug-resistant bacteria: Only use fidaxomicin for infection proven or strongly suspected to be caused by C. difficile. ( 5.3 )

5.1 Hypersensitivity Reactions Acute hypersensitivity reactions, including dyspnea, rash, pruritus, and angioedema of the mouth, throat, and face have been reported with fidaxomicin tablets. If a severe hypersensitivity reaction occurs, fidaxomicin tablets should be discontinued and appropriate therapy should be instituted. Some patients with hypersensitivity reactions to fidaxomicin tablets also reported a history of allergy to other macrolides. Physicians prescribing fidaxomicin tablets to patients with a known macrolide allergy should be aware of the possibility of hypersensitivity reactions.

5.2 Not for Use in Infections Other than C. difficile -Associated Diarrhea Fidaxomicin tablets are not expected to be effective for the treatment of other types of infections due to minimal systemic absorption of fidaxomicin [see Clinical Pharmacology ( 12.3 )] . Fidaxomicin tablets have not been studied for the treatment of infections other than CDAD. Fidaxomicin tablets should only be used for the treatment of CDAD.

5.3 Development of Drug-Resistant Bacteria Prescribing fidaxomicin tablets in the absence of proven or strongly suspected C. difficile infection is unlikely to provide benefit to the patient and increases the risk of the development of drug-resistant bacteria.

The most common adverse reactions in adults (incidence ≥2%) are nausea, vomiting, abdominal pain, gastrointestinal hemorrhage, anemia, and neutropenia. ( 6 ) To report SUSPECTED ADVERSE REACTIONS, contact Sandoz Inc., at 1-800-525-8747 or FDA at 1-800-FDA-1088 or www.fda.gov/medwatch .

6.1 Clinical Trials Experience Because clinical trials are conducted under widely varying conditions, adverse reaction rates observed in the clinical trials of a drug cannot be directly compared to rates in the clinical trials of another drug and may not reflect the rates observed in practice. Adults The safety of fidaxomicin 200 mg tablets taken twice a day for 10 days was evaluated in 564 adult patients with CDAD in two active-controlled trials with 86.7% of patients receiving a full course of treatment. Thirty-three adult patients receiving fidaxomicin (5.9%) withdrew from trials as a result of adverse reactions (AR). The types of AR resulting in withdrawal from the study varied considerably. Vomiting was the primary adverse reaction leading to discontinuation of dosing; this occurred at an incidence of 0.5% in both the fidaxomicin and vancomycin patients in Phase 3 trials. The most common selected adverse reactions occurring in ≥2% of adult patients treated with fidaxomicin are listed in Table 2 . Table 2: Selected Adverse Reactions with an Incidence of ≥2% Reported in Fidaxomicin-Treated Adult Patients in Controlled Trials System Organ Class Adverse Reaction Fidaxomicin (N=564) Vancomycin (N=583) n (%) n (%) Blood and Lymphatic System Disorders Anemia 14 (2%) 12 (2%) Neutropenia 14 (2%) 6 (1%) Gastrointestinal Disorders Nausea 62 (11%) 66 (11%) Vomiting 41 (7%) 37 (6%) Abdominal Pain 33 (6%) 23 (4%) Gastrointestinal Hemorrhage 20 (4%) 12 (2%) The following adverse reactions were reported in <2% of adult patients taking fidaxomicin tablets in controlled trials: Gastrointestinal Disorders: abdominal distension, abdominal tenderness, dyspepsia, dysphagia, flatulence, intestinal obstruction, megacolon Investigations: increased blood alkaline phosphatase, decreased blood bicarbonate, increased hepatic enzymes, decreased platelet count Metabolism and Nutrition Disorders: hyperglycemia, metabolic acidosis Skin and Subcutaneous Tissue Disorders: drug eruption, pruritus, rash

6.2 Post Marketing Experience The following adverse reactions have been identified during post-approval use of fidaxomicin tablets. Because these reactions are reported voluntarily from a population of uncertain size, it is not always possible to reliably estimate their frequency or establish a causal relationship to drug exposure. Hypersensitivity reactions (dyspnea, angioedema, rash, pruritus) Pediatric use information is approved for Cubist Pharmaceuticals LLC's DIFICID ® (fidaxomicin) tablets. However, due to Cubist Pharmaceuticals LLC's marketing exclusivity rights, this drug product is not labeled with that information.

Fidaxomicin and its main metabolite, OP-1118, are substrates of the efflux transporter, P-glycoprotein (P-gp), which is expressed in the gastrointestinal tract.

7.1 Cyclosporine Cyclosporine is an inhibitor of multiple transporters, including P-gp. When cyclosporine was co-administered with fidaxomicin, plasma concentrations of fidaxomicin and OP-1118 were significantly increased but remained in the ng/mL range [see Clinical Pharmacology ( 12.3 )] . Concentrations of fidaxomicin and OP-1118 may also be decreased at the site of action (i.e., gastrointestinal tract) via P-gp inhibition; however, concomitant P-gp inhibitor use had no attributable effect on safety or treatment outcome of fidaxomicin-treated adult patients in controlled clinical trials. Based on these results, fidaxomicin may be co-administered with P-gp inhibitors and no dose adjustment is recommended.

Pediatrics: The safety and effectiveness of fidaxomicin have not been established in pediatric patients younger than 6 months of age. (8.4) Pediatric use information is approved for Cubist Pharmaceuticals LLC's DIFICID ® (fidaxomicin) tablets. However, due to Cubist Pharmaceuticals LLC's marketing exclusivity rights, this drug product is not labeled with that information.

8.1 Pregnancy Risk Summary The limited available data on use of fidaxomicin in pregnant women are insufficient to inform any drug-associated risk for major birth defects, miscarriage or adverse maternal or fetal outcomes. Embryo-fetal reproduction studies in rats and rabbits dosed intravenously during organogenesis revealed no evidence of harm to the fetus at fidaxomicin and OP-1118 (its main metabolite) exposures 65-fold or higher than the clinical exposure at the fidaxomicin recommended dose [see Data]. The estimated background risk of major birth defects and miscarriage for the indicated populations 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 to 4% and 15 to 20%, respectively. Data Animal Data In pregnant rats, fidaxomicin was administered intravenously at doses of 4, 8, and 15 mg/kg/day from gestation day 6 through 17 (during the period of organogenesis). No embryo/fetal effects were noted in this study at exposures (AUC) 193-fold higher for fidaxomicin, and 65-fold higher for OP-1118 than the clinical exposure at the fidaxomicin recommended dose. In pregnant rabbits, fidaxomicin was administered intravenously at doses of 2, 4, and 7.5 mg/kg/day from gestation day 6 through 18 (during the period of organogenesis). No embryo/fetal effects were noted in this study at exposures 66-fold higher for fidaxomicin, and 245-fold higher for OP-1118 than the clinical exposure at the fidaxomicin recommended dose.

8.2 Lactation Risk Summary There is no information on the presence of fidaxomicin or its main metabolite, OP-1118, in human milk, the effects on the breastfed infant, or the effects on milk production. The developmental and health benefits of breastfeeding should be considered along with the mother’s clinical need for fidaxomicin and any potential adverse effects on the breastfed infant from fidaxomicin or from the underlying maternal condition.

8.4 Pediatric Use The safety and effectiveness of fidaxomicin have not been established in pediatric patients younger than 6 months of age. Pediatric use information is approved for Cubist Pharmaceuticals LLC's DIFICID ® (fidaxomicin) tablets. However, due to Cubist Pharmaceuticals LLC's marketing exclusivity rights, this drug product is not labeled with that information.

8.5 Geriatric Use Of the total number of patients in controlled trials of fidaxomicin, 50% were 65 years of age and over, while 31% were 75 and over. No overall differences in safety or effectiveness of fidaxomicin compared to vancomycin were observed between these subjects and younger subjects. In controlled trials, elderly patients (≥65 years of age) had higher plasma concentrations of fidaxomicin and its main metabolite, OP-1118, versus non-elderly patients (<65 years of age) [see Clinical Pharmacology ( 12.3 )] . However, greater exposures in elderly patients were not considered to be clinically significant. No dose adjustment is recommended for elderly patients.

Fidaxomicin is an antibacterial drug [see Microbiology ( 12.4 )] .