ZINPLAVA

5 WARNINGS AND PRECAUTIONS Heart Failure : Was reported more commonly in ZINPLAVA-treated patients with a history of congestive heart failure (CHF) in Trial 1 and Trial 2. In patients with a history of CHF, ZINPLAVA should be reserved for use when the benefit outweighs the risk. ( 5.1 ) 5.1 Heart Failure Heart failure was reported more commonly in Trial 1 and Trial 2 in ZINPLAVA-treated patients compared to placebo-treated patients. These adverse reactions occurred primarily in patients with underlying congestive heart failure (CHF). In patients with a history of CHF, 12.7% (15/118) of ZINPLAVA-treated patients and 4.8% (5/104) of placebo-treated patients had the serious adverse reaction of heart failure during the 12-week study period [see Adverse Reactions (6.1) ] . Additionally, in patients with a history of CHF, there were more deaths in ZINPLAVA-treated patients, 19.5% (23/118) than in placebo-treated patients, 12.5% (13/104) during the 12-week study period. The causes of death varied and included cardiac failure, infections, and respiratory failure. In patients with a history of CHF, ZINPLAVA should be reserved for use when the benefit outweighs the risk.

6 ADVERSE REACTIONS Adult Patients : The most common adverse reactions (reported in ≥4% of adult patients) included nausea, pyrexia, and headache. ( 6.1 ) Pediatric Patients : The most common adverse reactions (reported in >10% of pediatric patients) were pyrexia and headache ( 6.1 ) To report SUSPECTED ADVERSE REACTIONS, contact Merck Sharp & Dohme LLC at 1-877-888-4231 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. Clinical Trials Experience in Adults The safety of ZINPLAVA was evaluated in two placebo-controlled Phase 3 trials (Trial 1 n=390 and Trial 2 n=396). Patients received a single 10 mg/kg intravenous infusion of ZINPLAVA and concomitant standard of care (SoC) antibacterial drugs (metronidazole, vancomycin or fidaxomicin) for CDI. Adverse reactions reported within the first 4 weeks after ZINPLAVA was administered are described for the pooled Phase 3 trial population of 786 patients. The median age of patients receiving ZINPLAVA was 65 years (range 18 to 100), 50% were age 65 years or older, 56% were female, and 83% were white. Serious Adverse Reactions in Adults Serious adverse reactions occurring within 12 weeks following infusion were reported in 29% of ZINPLAVA-treated patients and 33% of placebo-treated patients. Heart failure was reported as a serious adverse reaction in 2.3% of the ZINPLAVA-treated patients and 1.0% of the placebo-treated patients [see Warnings and Precautions (5.1) ] . One patient discontinued the ZINPLAVA infusion due to ventricular tachyarrhythmia that occurred 30 minutes after the start of the infusion. Mortality rates were 7.1% and 7.6% in ZINPLAVA-treated patients and placebo-treated patients, respectively, during the 12-week follow-up period. Most Common Adverse Reactions in Adults The most common adverse reactions following treatment with ZINPLAVA (reported in ≥4% of patients within the first 4 weeks of infusion and with a frequency greater than placebo) were nausea, pyrexia, and headache (see Table 1 ). Table 1: Adverse Reactions Reported in ≥4% of ZINPLAVA-Treated Patients with CDI and at a Frequency Greater than Placebo in Trial 1 and Trial 2 All patients as treated population, defined as all randomized patients who received a dose of study medication, by treatment received , Adverse reactions reported within 4 weeks of administration of ZINPLAVA or placebo Adverse Reaction ZINPLAVA with SoC SoC = Standard of Care antibacterial drugs (metronidazole or vancomycin or fidaxomicin) for CDI N=786 % Placebo with SoC N=781 % Gastrointestinal disorders Nausea 7% 5% General disorders and administration site conditions Pyrexia 5% 3% Nervous system disorders Headache 4% 3% Infusion Related Adverse Reactions in Adults Overall, 10% of ZINPLAVA-treated patients experienced one or more infusion specific adverse reactions on the day of, or the day after, the infusion compared to 8% of placebo-treated patients. Infusion specific adverse reactions reported in ≥0.5% of patients receiving ZINPLAVA and at a frequency greater than placebo were nausea (3%), fatigue (1%), pyrexia (1%), dizziness (1%), headache (2%), dyspnea (1%) and hypertension (1%). Of these patients, 78% and 20% of patients experienced mild and moderate adverse reactions, respectively. These reactions resolved within 24 hours following onset. Clinical Trial Experience in Pediatric Patients The safety and pharmacokinetics of ZINPLAVA in pediatric patients 1 year of age and older were evaluated in a randomized, double-blind, placebo-controlled, multi-center trial (Trial 3). Enrolled patients had a diagnosis of CDI and received SoC (vancomycin, metronidazole, or fidaxomicin) for the baseline CDI episode. In this trial, 143 patients were randomized and treated, of whom 107 received a single infusion of ZINPLAVA (10 mg/kg) and 36 received a placebo infusion. Of these randomized patients, 58% were 1 to <12 years of age, 52% were male, 80% were white, and 7% were multi-racial. The majority (94%) of patients had one or more risk factors for CDI recurrence. [See Clinical Pharmacology (12.3) .] The adverse reactions observed in pediatric patients were comparable to those observed in adult patients. Five of 107 pediatric patients (5%) receiving ZINPLAVA and one of 36 pediatric patients receiving placebo (3%) died in Trial 3. There were no treatment discontinuations due to adverse reactions. The most common adverse reactions occurring in greater than 10% of pediatric patients treated with ZINPLAVA were pyrexia (19 patients, 18%) and headache (15 patients, 14%). One ZINPLAVA-treated pediatric patient (1%) experienced an infusion-related adverse reaction.

<table width="75%" ID="table1"><caption>Table 1: Adverse Reactions Reported in &#x2265;4% of ZINPLAVA-Treated Patients with CDI and at a Frequency Greater than Placebo in Trial 1 and Trial 2<footnote>All patients as treated population, defined as all randomized patients who received a dose of study medication, by treatment received</footnote>^,<footnote>Adverse reactions reported within 4 weeks of administration of ZINPLAVA or placebo</footnote></caption><col width="50%" align="left" valign="bottom"/><col width="25%" align="center" valign="bottom"/><col width="25%" align="center" valign="bottom"/><thead><tr><th valign="bottom" align="center" styleCode="Lrule Rrule">Adverse Reaction</th><th styleCode="Rrule">ZINPLAVA with SoC<footnote ID="t1f1">SoC = Standard of Care antibacterial drugs (metronidazole or vancomycin or fidaxomicin) for CDI</footnote> N=786 %</th><th styleCode="Rrule">Placebo with SoC<footnoteRef IDREF="t1f1"/> N=781 %</th></tr></thead><tbody><tr styleCode="Botrule"><td styleCode="Lrule Rrule" colspan="3"><content styleCode="bold">Gastrointestinal disorders</content></td></tr><tr styleCode="Botrule"><td styleCode="Lrule Rrule"> Nausea</td><td styleCode="Rrule">7%</td><td styleCode="Rrule">5%</td></tr><tr styleCode="Botrule"><td styleCode="Lrule Rrule" colspan="3"><content styleCode="bold">General disorders and administration site conditions</content></td></tr><tr styleCode="Botrule"><td styleCode="Lrule Rrule"> Pyrexia</td><td styleCode="Rrule">5%</td><td styleCode="Rrule">3%</td></tr><tr styleCode="Botrule"><td styleCode="Lrule Rrule" colspan="3"><content styleCode="bold">Nervous system disorders</content></td></tr><tr><td styleCode="Lrule Rrule"> Headache</td><td styleCode="Rrule">4%</td><td styleCode="Rrule">3%</td></tr></tbody></table>