New era in treatment for phenylketonuria: Pharmacologic therapy with sapropterin dihydrochloride

Oral administration of sapropterin hydrochloride, recently approved for use by the US Food and Drug Administration and the European Commission, is a novel approach for the treatment of phenylketonuria (PKU), one of the most common inborn errors of metabolism. PKU is caused by an inherited deficiency of the enzyme phenylalanine hydroxylase (PAH), and the pathophysiology of the disorder is related to chronic accumulation of the free amino acid phenylalanine in tissues. Contemporary therapy is based upon restriction of dietary protein intake, which leads to reduction of blood phenylalanine levels. This therapy is difficult to maintain throughout life, and dietary noncompliance is commonplace. Sapropterin dihydrochloride is a synthetic version of tetrahydrobiopterin, the naturally occurring pterin cofactor that is required for PAH-mediated phenylalanine hydroxylation. In a subset of individuals with PAH deficiency, sapropterin administration leads to reduction in blood phenylalanine levels independent of dietary protein. For these individuals, sapropterin is an effective novel therapy for PKU

State-of-the-art 2023 on gene therapy for phenylketonuria

Phenylketonuria (PKU) or hyperphenylalaninemia is considered a paradigm for an inherited (metabolic) liver defect and is, based on murine models that replicate all human pathology, an exemplar model for experimental studies on liver gene therapy. Variants in the PAH gene that lead to hyperphenylalaninemia are never fatal (although devastating if untreated), newborn screening has been available for two generations, and dietary treatment has been considered for a long time as therapeutic and satisfactory. However, significant shortcomings of contemporary dietary treatment of PKU remain. A long list of various gene therapeutic experimental approaches using the classical model for human PKU, the homozygous enu2/2 mouse, witnesses the value of this model to develop treatment for a genetic liver defect. The list of experiments for proof of principle includes recombinant viral (AdV, AAV, and LV) and non-viral (naked DNA or LNP-mRNA) vector delivery methods, combined with gene addition, genome, gene or base editing, and gene insertion or replacement. In addition, a list of current and planned clinical trials for PKU gene therapy is included. This review summarizes, compares, and evaluates the various approaches for the sake of scientific understanding and efficacy testing that may eventually pave the way for safe and efficient human application

Comparison of adeno-associated virus pseudotype 1, 2, and 8 vectors administered by intramuscular injection in the treatment of murine phenylketonuria

Phenylketonuria (PKU) is caused by hepatic phenylalanine hydroxylase (PAH) deficiency and is associated with systemic accumulation of phenylalanine (Phe). Previously we demonstrated correction of murine PKU after intravenous injection of a recombinant type 2 adeno-associated viral vector pseudotyped with type 8 capsid (rAAV2/8), which successfully directed hepatic transduction and Pah gene expression. Here, we report that liver PAH activity and phenylalanine clearance were also restored in PAH-deficient mice after simple intramuscular injection of either AAV2 pseudotype 1 (rAAV2/1) or rAAV2/8 vectors. Serotype 2 AAV vector (rAAV2/2) was also investigated, but long-term phenylalanine clearance has been observed only for pseudotypes 1 and 8. Therapeutic correction was shown in both male and female mice, albeit more effectively in males, in which correction lasted for the entire period of the experiment (>1 year). Although phenylalanine levels began to rise in female mice at about 8-10 months after rAAV2/8 injection they remained only mildly hyperphenylalaninemic thereafter and subsequent supplementation with synthetic tetrahydrobiopterin resulted in a transient decrease in blood phenylalanine. Alternatively, subsequent administration of a second vector with a different AAV pseudotype to avoid immunity against the previously administrated vector was also successful for long-term treatment of female PKU mice. Overall, this relatively less invasive gene transfer approach completes our previous studies and allows comparison of complementary strategies in the development of efficient PKU gene therapy protocols

Comparison of adeno-associated virus pseudotype1, 2, and 8 vectors administered by intramuscular injection in the treatment of murine phenylketonuria

Abstract Phenylketonuria (PKU) is caused by hepatic phenylalanine hydroxylase (PAH) deficiency and is associated with systemic accumulation of phenylalanine (Phe). Previously we demonstrated correction of murine PKU after intravenous injection of a recombinant type 2 adeno-associated viral vector pseudotyped with type 8 capsid (rAAV2=8), which successfully directed hepatic transduction and Pah gene expression. Here, we report that liver PAH activity and phenylalanine clearance were also restored in PAH-deficient mice after simple intramuscular injection of either AAV2 pseudotype 1 (rAAV2=1) or rAAV2=8 vectors. Serotype 2 AAV vector (rAAV2=2) was also investigated, but long-term phenylalanine clearance has been observed only for pseudotypes 1 and 8. Therapeutic correction was shown in both male and female mice, albeit more effectively in males, in which correction lasted for the entire period of the experiment (>1 year). Although phenylalanine levels began to rise in female mice at about 8-10 months after rAAV2=8 injection they remained only mildly hyperphenylalaninemic thereafter and subsequent supplementation with synthetic tetrahydrobiopterin resulted in a transient decrease in blood phenylalanine. Alternatively, subsequent administration of a second vector with a different AAV pseudotype to avoid immunity against the previously administrated vector was also successful for long-term treatment of female PKU mice. Overall, this relatively less invasive gene transfer approach completes our previous studies and allows comparison of complementary strategies in the development of efficient PKU gene therapy protocols

Modeling the cognitive effects of diet discontinuation in adults with phenylketonuria (PKU) using pegvaliase therapy in PAH-deficient mice

Existing phenylalanine hydroxylase (PAH)-deficient mice strains are useful models of untreated or late-treated human phenylketonuria (PKU), as most contemporary therapies can only be initiated after weaning and the pups have already suffered irreversible consequences of chronic hyperphenylalaninemia (HPA) during early brain development. Therefore, we sought to evaluate whether enzyme substitution therapy with pegvaliase initiated near birth and administered repetitively to C57Bl/6-Pahenu2/enu2 mice would prevent HPA-related behavioral and cognitive deficits and form a model for early-treated PKU. The main results of three reported experiments are: 1) lifelong weekly pegvaliase treatment prevented the cognitive deficits associated with HPA in contrast to persisting deficits in mice treated with pegvaliase only as adults. 2) Cognitive deficits reappear in mice treated with weekly pegvaliase from birth but in which pegvaliase is discontinued at 3 months age. 3) Twice weekly pegvaliase injection also prevented cognitive deficits but again cognitive deficits emerged in early-treated animals following discontinuation of pegvaliase treatment during adulthood, particularly in females. In all studies, pegvaliase treatment was associated with complete correction of brain monoamine neurotransmitter content and with improved overall growth of the mice as measured by body weight. Mean total brain weight however remained low in all PAH deficient mice regardless of treatment. Application of enzyme substitution therapy with pegvaliase, initiated near birth and continued into adulthood, to PAH-deficient Pahenu2/enu2 mice models contemporary early-treated human PKU. This model will be useful for exploring the differential pathophysiologic effects of HPA at different developmental stages of the murine brain. Keywords: Behavior; Cognition; Dopamine; Hyperphenylalaninemia; Pegvaliase; Phenylalanine hydroxylase; Phenylketonuria; Serotonin; Tryptophan; Tryptophan hydroxylase; Tyrosine; Tyrosine hydroxylase

Association of immune response with efficacy and safety outcomes in adults with phenylketonuria administered pegvaliase in phase 3 clinical trials

Background: This study assessed the immunogenicity of pegvaliase (recombinant Anabaena variabilis phenylalanine [Phe] ammonia lyase [PAL] conjugated with polyethylene glycol [PEG]) treatment in adults with phenylketonuria (PKU) and its impact on safety and efficacy. Methods: Immunogenicity was assessed during induction, upward titration, and maintenance dosing regimens in adults with PKU (n = 261). Total antidrug antibodies (ADA), neutralizing antibodies, immunoglobulin (Ig) M and IgG antibodies against PAL and PEG, IgG and IgM circulating immune complex (CIC) levels, complement components 3 and 4 (C3/C4), plasma Phe, and safety were assessed at baseline and throughout the study. Pegvaliase-specific IgE levels were measured in patients after hypersensitivity adverse events (HAE). Findings: All patients developed ADA against PAL, peaking by 6 months and then stabilizing. Most developed transient antibody responses against PEG, peaking by 3 months, then returning to baseline by 9 months. Binding of ADA to pegvaliase led to CIC formation and complement activation, which were highest during early treatment. Blood Phe decreased over time as CIC levels and complement activation declined and pegvaliase dosage increased. HAEs were most frequent during early treatment and declined over time. No patient with acute systemic hypersensitivity events tested positive for pegvaliase-specific IgE near the time of the event. Laboratory evidence was consistent with immune complex-mediated type III hypersensitivity. No evidence of pegvaliase-associated IC-mediated end organ damage was noted. Interpretation: Despite a universal ADA response post-pegvaliase administration, adult patients with PKU achieved substantial and sustained blood Phe reductions with a manageable safety profile. Fund: BioMarin Pharmaceutical Inc. Keywords: Enzyme replacement therapy, Antidrug antibody, Circulating immune complex, Hypersensitivity, Phenylalanin

Long-Term Outcomes and Practical Considerations in the Pharmacological Management of Tyrosinemia Type 1

Tyrosinemia type 1 (TT1) is a rare metabolic disease caused by a defect in tyrosine catabolism. TT1 is clinically characterized by acute liver failure, development of hepatocellular carcinoma, renal and neurological problems, and consequently an extremely poor outcome. This review showed that the introduction of 2-(2-nitro-4-trifluoromethylbenzoyl)-1,3-cyclohexanedione (NTBC) in 1992 has revolutionized the outcome of TT1 patients, especially when started pre-clinically. If started early, NTBC can prevent liver failure, renal problems, and neurological attacks and decrease the risk for hepatocellular carcinoma. NTBC has been shown to be safe and well tolerated, although the long-term effectiveness of treatment with NTBC needs to be awaited. The high tyrosine concentrations caused by treatment with NTBC could result in ophthalmological and skin problems and requires life-long dietary restriction of tyrosine and its precursor phenylalanine, which could be strenuous to adhere to. In addition, neurocognitive problems have been reported since the introduction of NTBC, with hypothesized but as yet unproven pathophysiological mechanisms. Further research should be done to investigate the possible relationship between important clinical outcomes and blood concentrations of biochemical parameters such as phenylalanine, tyrosine, succinylacetone, and NTBC, and to develop clear guidelines for treatment and follow-up with reliable measurements. This all in order to ultimately improve the combined NTBC and dietary treatment and limit possible complications such as hepatocellular carcinoma development, neurocognitive problems, and impaired quality of life

Pegvaliase for the treatment of phenylketonuria: A pivotal, double-blind randomized discontinuation Phase 3 clinical trial

Introduction Pegvaliase is a recombinant Anabaena variabilis phenylalanine ammonia lyase (PAL) enzyme under investigation for treatment of adult phenylketonuria (PKU). This manuscript describes results of a randomized discontinuation trial (RDT) designed to evaluate the effects of pegvaliase treatment on blood phenylalanine (Phe) and neuropsychiatric outcomes in adults with PKU. Methods PRISM-2 is a 4-part, Phase 3 study that enrolled adults with PKU receiving pegvaliase treatment (initiated in a prior Phase 2 or Phase 3 study). The RDT, Part 2 of PRISM-2, was an 8-week trial that evaluated change in blood Phe concentrations, neuropsychiatric and neurocognitive measures, and safety outcomes in PRISM-2 participants who had achieved at least a 20% blood Phe reduction from pre-treatment baseline with pegvaliase treatment. Participants were randomized 2:1 to either continue pegvaliase (20 mg/day or 40 mg/day) or switch to matching placebo. Results The pooled pegvaliase group enrolled 66 participants and each placebo group enrolled 14 participants. The primary endpoint of change in blood Phe concentration from RDT entry to RDT Week 8 was met with clinically meaningful and statistically significant differences between the pegvaliase and placebo groups. Mean (SD) blood Phe at the beginning of the RDT when all participants were receiving pegvaliase was 563.9 μM (504.6) in the group assigned to the 20 mg/day placebo group (n = 14), 508.2 μM (363.7) in those assigned to the 40 mg/day placebo group (n = 14), and 503.9 μM (520.3) in those assigned to continue pegvaliase treatment (n = 58). At Week 8 of the RDT, the least squares mean change (95% confidence interval) in blood Phe was 949.8 μM (760.4 to 1139.1) for the 20 mg/day placebo group and 664.8 μM (465.5 to 864.1) for the 40 mg/day placebo group in comparison to 26.5 μM (−68.3 to 121.3) for the pooled (20 mg/day and 40 mg/day) pegvaliase group (P < 0.0001 for pooled pegvaliase group vs each placebo group). Adverse events (AEs) were usually lower in the pooled placebo group when compared to the pooled pegvaliase group. The most common AEs for the pooled pegvaliase and pooled placebo groups were arthralgia (13.6% and 10.3%, respectively), headache (12.1% and 24.1%), anxiety (10.6% and 6.9%), fatigue (10.6% and 10.3%), and upper respiratory tract infection (1.5% and 17.2%). Conclusion Mean blood Phe reduction was sustained in the pegvaliase group, while placebo groups had mean blood Phe concentration increase toward pre-treatment baseline levels. Results from this study confirmed the efficacy of pegvaliase in maintaining reduced blood Phe concentrations with a manageable safety profile for most participants

Development of international consensus recommendations using a modified Delphi approach

Funding Information: This work was supported by BioMarin Pharmaceutical Inc . Funding Information: The content of this manuscript was based on preparatory pre-meeting activities and presentations and discussions during two advisory board meetings that were coordinated and funded by BioMarin Pharmaceutical Inc. All authors or their institutions received funding from BioMarin to attend at least one or both meetings. Additional disclosures: BKB received consulting payments from BioMarin, Shire, Genzyme, Alexion, Horizon Therapeutics, Denali Therapeutics, JCR Pharma, Moderna, Aeglea BioTherapeutics, SIO Gene Therapies, Taysha Gene Therapy, Ultragenyx, and Inventiva Pharma, participated as clinical trial investigator for BioMarin, Shire, Denali Therapeutics, Homology Medicines, Ultragenyx, and Moderna as well as received speaker fees from BioMarin, Shire, Genzyme, and Horizon Therapeutics. AH received consulting payments from BioMarin, Chiesi, Shire, Genzyme, Amicus, and Ultragenyx, participated as clinical trial investigator for Ultragenyx as well as received speaker fees from Alexion, Amicus, BioMarin, Genzyme, Nutricia, Sobi, and Takeda. ABQ received consulting payments from BioMarin, speaker fees from BioMarin, Nutricia, Vitaflo, Sanofi, Takeda, Recordati, and travel support from Vitaflo . SEC received consulting payments and speaker fees from BioMarin as well as consulting payments from Synlogic Therapeutics. COH was clinical trial investigator for BioMarin and received consulting and speaker payments from BioMarin. SCJH received consulting payments and travel support from BioMarin and Homology Medicines. NL received consulting payments from Alnylam, Amicus, Astellas, BioMarin, BridgeBio, Chiesi, Genzyme/Sanofi, HemoShear, Horizon Therapeutics, Jaguar, Moderna, Nestle, PTC Therapeutics, Reneo, Shire, Synlogic, and Ultragenyx, participated as clinical trial investigator for Aeglea, Amicus, Astellas, BioMarin, Genzyme/Sanofi, Homology, Horizon, Moderna, Pfizer, Protalix, PTC Therapeutics, Reneo, Retrophin/Travere therapeutics, Shire, and Ultragenyx, as well as received speaker fees from Cycle Pharmaceuticals, Leadiant and Recordati. MCM II received consulting payments from BioMarin, Horizon Therapeutics, Rhythm Pharmaceuticals, Applied Therapeutics, Cycle Therapeutics, and Ultragenyx. ALSP received speaker fees from BioMarin. JCR received consulting payments from Applied Pharma Research, Merck Serono, BioMarin, Vitaflo, and Nutricia, speaker fees from Applied Pharma Research, Merck Serono, BioMarin Pharmaceutical, Vitaflo, Cambrooke, PIAM, LifeDiet, and Nutricia, as well as travel support from Applied Pharma Research, Merck Serono, BioMarin, Vitaflo, Cambrooke, PIAM, and Nutricia. SS received consulting payments, research grants, speaker fees, and travel support from BioMarin and participated as clinical trials investigator for BioMarin. ASV received consulting payments from BioMarin, Horizon Therapeutics, and Ultragenyx and participated as clinical trial investigator for Acadia, Alexion, BioMarin, Genzyme, Homology Medicines, Kaleido, Mallinckrodt, and Ultragenyx. JV received consulting payments from BioMarin, LogicBio Pharmaceuticals, Sangamo Therapeutics, Orphan Labs, Synlogic Therapeutics, Sanofi, Axcella Health, Agios Pharmaceuticals, and Applied Therapeutics as well as travel grants from BioMarin and LogicBio Pharmaceuticals. MW received consulting payments, speaker fees, and travel support from BioMarin, and participated as clinical trial investigator for Mallinckrodt, Roche, Wave, Cycle Therapeutics, and Intrabio. ACM participated in strategic advisory boards and received honoraria as a consultant and as a speaker for Merck Serono, BioMarin, Nestlé Health Science (SHS), Applied Pharma Research, Actelion, Retrophin, Censa, PTC Therapeutics, and Arla Food. Funding Information: Ideally, access to (neuro)psychological/psychiatric support should assist adolescents with identifying, understanding, and reporting of PKU-specific challenges (Table 3), offering individualized recommendations on managing these challenges. Although there is no replacement for mental health services for patients with identified needs, psychosocial support from PKU peers, e.g., through PKU camps, virtual social events, etc., can at least in the short-term help to improve metabolic control by providing individuals an opportunity to participate in supportive PKU-related educational activities potentially reducing perceived social isolation [91]. In addition to PKU camps, which may be very specific to certain regions or countries, HCPs should consider encouraging involvement in local, regional, national and international PKU patient/family advocacy and social support organizations, introducing adolescents and young adults to national/international patient registries [92,93]. Besides support from PKU peers, patients can benefit from non-PKU peer support, although some adolescents and young adults with PKU may not disclose to others and may avoid eating in with others or eating in public due to potential feelings of anxiety or feelings of being ashamed of their disease. In addition, patients with PKU of all ages, but particularly vulnerable adolescents and young adults, can benefit from having the opportunity to learn about and practice strategies that help promote feelings of empowerment and self-efficacy that can be used in both familiar and unfamiliar environments where they may experience peer pressure and feel the need to ‘fit in’. For example, a role-play approach involving behavioral rehearsal, self-monitoring, goal setting, and training in problem-solving skills with emphasis on initiation and inhibition (i.e., how to say no) could be provided by parents, PKU peers, or even members of the PKU team. These types of activities can be used to teach adolescents with PKU how to react in social situations, such as dining out, helping to avoid indulging and increased risk-taking behavior, a hallmark of the adolescent period [94].This work was supported by BioMarin Pharmaceutical Inc.The content of this manuscript was based on preparatory pre-meeting activities and presentations and discussions during two advisory board meetings that were coordinated and funded by BioMarin Pharmaceutical Inc. All authors or their institutions received funding from BioMarin to attend at least one or both meetings. Additional disclosures: BKB received consulting payments from BioMarin, Shire, Genzyme, Alexion, Horizon Therapeutics, Denali Therapeutics, JCR Pharma, Moderna, Aeglea BioTherapeutics, SIO Gene Therapies, Taysha Gene Therapy, Ultragenyx, and Inventiva Pharma, participated as clinical trial investigator for BioMarin, Shire, Denali Therapeutics, Homology Medicines, Ultragenyx, and Moderna as well as received speaker fees from BioMarin, Shire, Genzyme, and Horizon Therapeutics. AH received consulting payments from BioMarin, Chiesi, Shire, Genzyme, Amicus, and Ultragenyx, participated as clinical trial investigator for Ultragenyx as well as received speaker fees from Alexion, Amicus, BioMarin, Genzyme, Nutricia, Sobi, and Takeda. ABQ received consulting payments from BioMarin, speaker fees from BioMarin, Nutricia, Vitaflo, Sanofi, Takeda, Recordati, and travel support from Vitaflo. SEC received consulting payments and speaker fees from BioMarin as well as consulting payments from Synlogic Therapeutics. COH was clinical trial investigator for BioMarin and received consulting and speaker payments from BioMarin. SCJH received consulting payments and travel support from BioMarin and Homology Medicines. NL received consulting payments from Alnylam, Amicus, Astellas, BioMarin, BridgeBio, Chiesi, Genzyme/Sanofi, HemoShear, Horizon Therapeutics, Jaguar, Moderna, Nestle, PTC Therapeutics, Reneo, Shire, Synlogic, and Ultragenyx, participated as clinical trial investigator for Aeglea, Amicus, Astellas, BioMarin, Genzyme/Sanofi, Homology, Horizon, Moderna, Pfizer, Protalix, PTC Therapeutics, Reneo, Retrophin/Travere therapeutics, Shire, and Ultragenyx, as well as received speaker fees from Cycle Pharmaceuticals, Leadiant and Recordati. MCM II received consulting payments from BioMarin, Horizon Therapeutics, Rhythm Pharmaceuticals, Applied Therapeutics, Cycle Therapeutics, and Ultragenyx. ALSP received speaker fees from BioMarin. JCR received consulting payments from Applied Pharma Research, Merck Serono, BioMarin, Vitaflo, and Nutricia, speaker fees from Applied Pharma Research, Merck Serono, BioMarin Pharmaceutical, Vitaflo, Cambrooke, PIAM, LifeDiet, and Nutricia, as well as travel support from Applied Pharma Research, Merck Serono, BioMarin, Vitaflo, Cambrooke, PIAM, and Nutricia. SS received consulting payments, research grants, speaker fees, and travel support from BioMarin and participated as clinical trials investigator for BioMarin. ASV received consulting payments from BioMarin, Horizon Therapeutics, and Ultragenyx and participated as clinical trial investigator for Acadia, Alexion, BioMarin, Genzyme, Homology Medicines, Kaleido, Mallinckrodt, and Ultragenyx. JV received consulting payments from BioMarin, LogicBio Pharmaceuticals, Sangamo Therapeutics, Orphan Labs, Synlogic Therapeutics, Sanofi, Axcella Health, Agios Pharmaceuticals, and Applied Therapeutics as well as travel grants from BioMarin and LogicBio Pharmaceuticals. MW received consulting payments, speaker fees, and travel support from BioMarin, and participated as clinical trial investigator for Mallinckrodt, Roche, Wave, Cycle Therapeutics, and Intrabio. ACM participated in strategic advisory boards and received honoraria as a consultant and as a speaker for Merck Serono, BioMarin, Nestlé Health Science (SHS), Applied Pharma Research, Actelion, Retrophin, Censa, PTC Therapeutics, and Arla Food. Publisher Copyright: © 2022 The AuthorsBackground: Early treated patients with phenylketonuria (PKU) often become lost to follow-up from adolescence onwards due to the historical focus of PKU care on the pediatric population and lack of programs facilitating the transition to adulthood. As a result, evidence on the management of adolescents and young adults with PKU is limited. Methods: Two meetings were held with a multidisciplinary international panel of 25 experts in PKU and comorbidities frequently experienced by patients with PKU. Based on the outcomes of the first meeting, a set of statements were developed. During the second meeting, these statements were voted on for consensus generation (≥70% agreement), using a modified Delphi approach. Results: A total of 37 consensus recommendations were developed across five areas that were deemed important in the management of adolescents and young adults with PKU: (1) general physical health, (2) mental health and neurocognitive functioning, (3) blood Phe target range, (4) PKU-specific challenges, and (5) transition to adult care. The consensus recommendations reflect the personal opinions and experiences from the participating experts supported with evidence when available. Overall, clinicians managing adolescents and young adults with PKU should be aware of the wide variety of PKU-associated comorbidities, initiating screening at an early age. In addition, management of adolescents/young adults should be a joint effort between the patient, clinical center, and parents/caregivers supporting adolescents with gradually gaining independent control of their disease during the transition to adulthood. Conclusions: A multidisciplinary international group of experts used a modified Delphi approach to develop a set of consensus recommendations with the aim of providing guidance and offering tools to clinics to aid with supporting adolescents and young adults with PKU.publishersversionpublishe

Generating a taxonomy for genetic conditions relevant to reproductive planning

As genome or exome sequencing (hereafter genome-scale sequencing) becomes more integrated into standard care, carrier testing is an important possible application. Carrier testing using genome-scale sequencing can identify a large number of conditions, but choosing which conditions/genes to evaluate as well as which results to disclose can be complicated. Carrier testing generally occurs in the context of reproductive decision-making and involves patient values in a way that other types of genetic testing may not. The Kaiser Permanente Clinical Sequencing Exploratory Research program is conducting a randomized clinical trial of preconception carrier testing that allows participants to select their preferences for results from among broad descriptive categories rather than selecting individual conditions. This paper describes 1) the criteria developed by the research team, the return of results committee (RORC), and stakeholders for defining the categories; 2) the process of refining the categories based on input from patient focus groups and validation through a patient survey; and, 3) how the RORC then assigned specific gene-condition pairs to taxonomy categories being piloted in the trial. The development of four categories (serious, moderate/mild, unpredictable, late onset) for sharing results allows patients to select results based on their values without separately deciding their interest in knowing their carrier status for hundreds of conditions. A fifth category, lifespan limiting, was always shared. The lessons learned may be applicable in other results disclosure situations, such as incidental findings