Patisiran

Dosage Forms

Excipient information presented when available (limited, particularly for generics); consult specific product labeling.

Solution, Intravenous [preservative free]:

Onpattro: 10 mg/5 mL (5 mL)

Pharmacology

Mechanism of Action

Patisiran is a double-stranded small interfering ribonucleic acid (siRNA) that causes degradation of mutant and wild-type transthyretin (TTR) mRNA through RNA interference, which results in a reduction of serum TTR protein and TTR protein deposits in tissues. Serum TTR is a carrier of retinol binding protein, which is involved in the transport of vitamin A in the blood.

Pharmacokinetics/Pharmacodynamics

Distribution

V_dss: 0.26 ± 0.2 L/kg

Metabolism

By nucleases to nucleotides of various lengths

Excretion

Urine: <1% as unchanged drug

Onset of Action

10 to 14 days (mean serum TTR reduced by ~80%)

Half-Life Elimination

3.2 ± 1.8 days

Protein Binding

Plasma protein: ≤2.1% (albumin and human alpha1-acid glycoprotein)

Use: Labeled Indications

Polyneuropathy: Treatment of the polyneuropathy of hereditary transthyretin-mediated amyloidosis in adults.

Contraindications

There are no contraindications listed in the US manufacturer's labeling.

Canadian labeling: Severe hypersensitivity (eg, anaphylaxis) to patisiran or any component of the formulation.

Dosage and Administration

Dosing: Adult

Note: At least 60 minutes prior to administration of patisiran, premedicate with a corticosteroid, acetaminophen, an H₁ blocker, and an H₂ blocker to reduce the risk of infusion-related reactions (IRR).

Polyneuropathy: IV: Base dose on actual body weight.

<100 kg: 0.3 mg/kg once every 3 weeks

≥100 kg: 30 mg once every 3 weeks

Missed dose:

Within 3 days of missed dose: Administer dose, then continue dosing according to original schedule.

More than 3 days after missed dose: Administer dose, then continue dosing every 3 weeks thereafter.

Dosing: Geriatric

Refer to adult dosing.

Dosing: Adjustment for Toxicity

Infusion-related reactions (IRR): Consider slowing or discontinuing the infusion and resume at a slower infusion rate when symptoms have resolved; consider additional or higher doses of premedication in these patients during subsequent infusions to reduce IRR risk. If a serious of life-threatening IRR occurs, discontinue and do not readminister.

Reconstitution

Remove from refrigeration and allow to come to room temperature. Do not shake. Based on calculated dosage, withdraw the entire contents of one or more vials into a syringe. Filter through a sterile 0.45 micron polyethersulfone syringe filter into a sterile container. Withdraw the required volume of filtered solution using a syringe. Add to a DEHP-free infusion bag containing NS for a total volume of 200 mL. Gently invert the bag; do not shake. Do not mix or dilute with other drugs.

Administration

IV: Following dilution and filtering, administer through a dedicated free-flowing venous access line with a DEHP-free infusion set containing a 1.2 micron polyethersulfone (PES) in-line infusion filter. Infuse over ~80 minutes, with an initial infusion rate of 1 mL/minute for 15 minutes, then increase to ~3 mL/minute for the remainder of the infusion (may extend duration of infusion >80 minutes to manage or prevent infusion-related reactions. After infusion is complete, flush IV administration set with NS. Monitor infusion site for infiltration and manage suspected extravasation using local standard practice for nonvesicants.

Storage

Store intact vials at 2°C to 8°C (36°F to 46°F). Do not freeze. Discard if frozen. If refrigeration is not available, store at room temperature ≤25°C (≤77°F) for ≤14 days. After dilution and filtration, discard any unused drug. Administer immediately after preparation, or store in infusion bag at room temperature (≤30°C [≤86°F]) for up to 16 hours, including infusion time.

Drug Interactions

There are no known significant interactions.

Adverse Reactions

>10%:

Respiratory: Upper respiratory tract infection (29%)

Miscellaneous: Infusion related reaction (19%)

1% to 10%:

Cardiovascular: Atrioventricular block (3%), flushing (>2%)

Central nervous system: Vertigo (5%)

Dermatologic: Erythema (7%)

Gastrointestinal: Dyspepsia (8%), abdominal pain (>2%), nausea (>2%)

Neuromuscular & skeletal: Muscle spasm (8%), arthralgia (7%), back pain (>2%)

Ophthalmic: Keratoconjunctivitis sicca (5%), blurred vision (3%), visual disturbance (2%)

Respiratory: Dyspnea (8%), bronchitis (7%)

<1%, postmarketing, and/or case reports: Hypotension, injection site extravasation, syncope, vitamin A deficiency

Warnings/Precautions

Concerns related to adverse effects:

• Infusion-related reactions: Infusion-related reactions (IRR) have been reported, with a majority occurring within the first 2 infusions and the frequency decreasing with additional infusions. Common symptoms included abdominal, back or chest pain, dyspnea, facial edema, flushing, headache, nausea, rash and tachycardia. Premedicate with a corticosteroid, acetaminophen, and antihistamines (H₁ and H₂ blockers). Monitor closely; if an IRR occurs, consider slowing or interrupting the infusion. If interrupted, wait until symptoms have resolved before resuming the infusion at a slower rate. With future infusions, consider a slower infusion rate or higher doses of premedications. If a serious IRR occurs, stop the infusion and do not resume.
• Reduced vitamin A levels: A decrease in serum vitamin A has been reported with patisiran treatment. Supplement at the recommended daily allowance (RDA) of vitamin A during treatment. Do not administer doses higher than the RDA; serum vitamin A levels do not reflect the total vitamin A in the body. If ocular symptoms such as night blindness develop, refer the patient to an ophthalmologist.

Monitoring Parameters

Infusion-related reactions; ocular symptoms indicative of vitamin A deficiency (eg, night blindness)

Pregnancy

Pregnancy Considerations

Adverse events were observed in some animal reproduction studies.

Patisiran decreases serum concentrations of vitamin A which is required for normal fetal development. The effects to the fetus of maternal vitamin A supplementation during patisiran therapy, or the effects to the fetus of reducing maternal serum transthyretin are not known.

Patient Education

• Discuss specific use of drug and side effects with patient as it relates to treatment. (HCAHPS: During this hospital stay, were you given any medicine that you had not taken before? Before giving you any new medicine, how often did hospital staff tell you what the medicine was for? How often did hospital staff describe possible side effects in a way you could understand?)
• Patient may experience common cold symptoms, nausea, muscle spasm, joint pain, redness, or dizziness. Have patient report immediately to prescriber signs of infusion reaction, vision changes, poor night vision, shortness of breath, severe injection site redness, burning, pain, edema, or irritation (HCAHPS).
• Educate patient about signs of a significant reaction (eg, wheezing; chest tightness; fever; itching; bad cough; blue skin color; seizures; or swelling of face, lips, tongue, or throat). Note: This is not a comprehensive list of all side effects. Patient should consult prescriber for additional questions.

Intended Use and Disclaimer: Should not be printed and given to patients. This information is intended to serve as a concise initial reference for health care professionals to use when discussing medications with a patient. You must ultimately rely on your own discretion, experience, and judgment in diagnosing, treating, and advising patients.