Circulating antibodies that specifically bind polyethylene glycol (PEG), a polymer routinely used in protein and nanoparticle therapeutics, have been associated with reduced efficacy and increased adverse reactions to some PEGylated therapeutics. In addition to acute induction of anti-PEG antibodies (APA) by PEGylated drugs, typically low but detectable levels of APA are also found in up to 70% of the general population. Despite the broad implications of APA, the dynamics of APA-mediated clearance of PEGylated drugs, and why many patients continue to respond to PEGylated drugs despite the presence of pre-existing APA, remains not well understood. Here, we developed a minimal physiologically based pharmacokinetic (mPBPK) model that incorporates various properties of APA and PEGylated drugs. Our mPBPK model reproduced clinical PK data of APA-mediated accelerated blood clearance of pegloticase, as well as APA-dependent elimination of PEGyated liposomes in mice. Our model predicts that the prolonged circulation of PEGylated drugs will be compromised only at APA concentrations greater than ~500 ng/mL, providing a quantitative explanation to why the effects of APA on PEGylated treatments appear to be limited in most patients. This mPBPK model is readily adaptable to other PEGylated drugs and particles to predict the precise levels of APA that could render them ineffective, providing a powerful tool to support the development and interpretation of preclinical and clinical studies of various PEGylated therapeutics.

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Objective: To review the pharmacological characteristics, clinical evidence, and place in therapy of voxelotor for the treatment of sickle cell disease (SCD). Data Sources: A comprehensive literature search of PubMed (1966 to April 2020) was conducted. Key search terms included GBT440, sickle cell, and voxelotor. Other sources were derived from bibliographies of articles, product labeling, manufacturer’s website, and news releases. ClinicalTrials.gov was searched for additional studies. Study Selection and Data Extraction: All English-language articles identified from the data sources were reviewed and evaluated. Case reports/series and phase 1 through 3 clinical trials were included. Data Synthesis: SCD is an inherited disorder associated with significant morbidity and early mortality. Three medications approved for SCD reduce SCD-associated complications but do not selectively ameliorate the underlying disease. Voxelotor is a novel agent that targets the pathophysiology of SCD. A phase 3 trial reported an increase in mean Hb level from baseline for voxelotor compared with placebo (1.1 vs −0.1 g/dL; P < 0.001). Voxelotor is generally well tolerated, with common adverse effects including headache, diarrhea, nausea, and arthralgia. Relevance to Patient Care and Clinical Practice: Voxelotor may be considered for patients with SCD who have continued anemia and hemolysis despite being on maximum tolerated dose of hydroxyurea or in those who are hydroxyurea intolerant. Voxelotor is costly; therefore, both cost and benefit should be weighed before prescribing. Conclusion: Voxelotor appears to be safe and effective as monotherapy or in combination with hydroxyurea for patients with SCD who are 12 years of age and older.