In clinical trials of Palynziq with induction/titration/maintenance dosing, 29 out of 285 (10%) patients experienced a total of 42 anaphylaxis episodes [see Adverse Reactions (6.1, 6.2)]. The exposure-adjusted rate of anaphylaxis was highest during the induction and titration phases (0.25 episodes/person‑years; 5% of patients with at least one episode) and decreased in the maintenance phase (0.05 episodes/person‑years; 7% of patients with at least one episode). Signs and symptoms of anaphylaxis reported in clinical trials of Palynziq included syncope, hypotension, hypoxia, dyspnea, wheezing, chest discomfort/chest tightness, tachycardia, angioedema (swelling of face, lips, eyes, tongue), throat tightness, skin flushing, rash, urticaria, pruritus, and gastrointestinal symptoms (vomiting, nausea, diarrhea). In clinical trials of Palynziq, anaphylaxis generally occurred within 1 hour after injection (81%; 34/42 episodes); however, delayed episodes also occurred up to 48 hours after Palynziq administration. Most episodes of anaphylaxis occurred within the first year of dosing (69%, 29/42 episodes), but cases also occurred after one year of dosing and up to 1604 days (4.4 years) into treatment. Management of anaphylaxis in Palynziq clinical trials included: administration of auto-injectable epinephrine (48%; 20/42 episodes), corticosteroids (55%; 23/42 episodes), antihistamines (57%; 24/42 episodes), and/or oxygen (5%; 2/42 episodes). Twenty one out of the 29 (72%) patients who experienced anaphylaxis were rechallenged with Palynziq and 6 out of the 21 patients who were rechallenged (29%) had recurrence of anaphylaxis. All anaphylaxis episodes resolved without sequelae. 

Consider having an adult observer for patients who may need assistance in recognizing and managing anaphylaxis during Palynziq treatment. If an adult observer is needed, the observer should be present during and for at least 60 minutes after Palynziq administration, should be able to administer auto‑injectable epinephrine, and to call for emergency medical support upon its use.

Anaphylaxis requires immediate treatment with auto-injectable epinephrine. Prescribe auto‑injectable epinephrine to all patients receiving Palynziq and instruct patients to carry auto‑injectable epinephrine with them at all times during Palynziq treatment. Prior to the first dose, instruct the patient and observer (if applicable) on how to recognize the signs and symptoms of anaphylaxis, how to properly administer auto‑injectable epinephrine, and to seek immediate medical care upon its use. Consider the risks associated with auto-injectable epinephrine use when prescribing Palynziq. Refer to the auto‑injectable epinephrine prescribing information for complete information. 

Consider the risks and benefits of readministering Palynziq following an episode of anaphylaxis. If the decision is made to readminister Palynziq, administer the first dose under the supervision of a healthcare provider equipped to manage anaphylaxis and closely observe the patient for at least 60 minutes following the dose. Subsequent Palynziq dose titration should be based on patient tolerability and therapeutic response [see Dosage and Administration (2.4)].

Consider premedication with an H1-receptor antagonist, H2-receptor antagonist, and/or antipyretic prior to Palynziq administration based upon individual patient tolerability [see Dosage and Administration (2.3)].

Palynziq is available only through a restricted program under a REMS [see Warnings and Precautions (5.2)].