Rusfertide: Side Effects

Safety Overview#

Rusfertide has been evaluated in phase 1 healthy volunteer studies, the phase 2 REVIVE trial (70 patients), and the phase 3 VERIFY trial (285+ patients). The overall safety profile is characterized by frequent but generally mild injection site reactions and pharmacologically expected effects of iron restriction. No serious adverse events have been attributed to rusfertide across the clinical program.

Injection Site Reactions#

Injection site reactions are the most common adverse event and the defining safety characteristic of rusfertide treatment:

• Frequency: Approximately 48-56% of patients across trials
• Severity: Predominantly grade 1-2 (mild to moderate)
• Manifestations: Redness, itching, induration, swelling at the injection site
• Temporal pattern: More common in early treatment; tend to decrease from week 32 to 52, suggesting adaptation over time
• Management: Site rotation; no treatment discontinuation required in most cases

Iron Restriction Effects#

As a pharmacological consequence of ferroportin degradation, rusfertide restricts systemic iron availability:

Anemia#

• Reported in approximately 26% of patients
• Expected effect of the mechanism of action
• Usually mild and manageable with dose adjustment
• Distinct from PV-related erythrocytosis -- represents appropriate iron restriction

Iron Parameters#

• Reduction in serum iron and transferrin saturation (intended pharmacodynamic effect)
• Ferritin levels should be monitored to avoid excessive iron depletion
• Dose reduction indicated if clinically significant iron deficiency develops

Fatigue#

Fatigue was reported in approximately 20% of treated patients. Notably, PV-related fatigue often improved with rusfertide treatment (as demonstrated by PROMIS Fatigue scores in the VERIFY trial), suggesting that some fatigue may be related to the underlying disease rather than drug effect.

Adverse Event Summary#

Safety in Special Contexts#

Concomitant Cytoreductive Therapy#

Rusfertide has been used safely alongside:

• Hydroxyurea
• Ruxolitinib
• Interferon alfa

Similar dosing requirements and safety profiles were observed regardless of concomitant cytoreductive therapy.

Treatment Interruption and Reinitiation#

• Interrupting rusfertide leads to loss of hematocrit control (hematocrit rises, phlebotomy requirements return)
• Reinitiating treatment restores therapeutic benefit
• No rebound or safety concerns with treatment interruption/reinitiation cycles

Contraindications#

• Severe iron deficiency anemia: Rusfertide restricts iron availability and could worsen pre-existing iron deficiency
• Hypersensitivity: Known allergy to rusfertide or excipients

Drug Interactions#

No clinically significant drug interactions have been identified. Rusfertide has been used in combination with:

• Cytoreductive therapies (hydroxyurea, ruxolitinib, interferon)
• Therapeutic phlebotomy
• Other standard PV management strategies

Related Reading#

• Rusfertide overview and research guide
• Rusfertide dosing protocols
• Rusfertide risks and legal status