Pegvaliase therapy for phenylketonuria: Real-world case series and clinical insights

OBJECTIVE

The aim of this study is to present a series of case studies on the real-life use of pegvaliase in Italy in managing patients affected by phenylketonuria (PKU) and provide practical insight and support to healthcare professionals currently approaching and facing this novel enzyme substitution therapy.

METHODS

A panel of 11 PKU experts from seven leading Italian treatment centers attended online virtual meetings with the aim of reviewing their clinical and practical experiences with pegvaliase based on occurred cases. In selecting the cases, specific consideration was given to the nationwide representation of the centers involved and to the number of patients with PKU managed. Cases were thoroughly reviewed, with comprehensive discussions enabling the identification of key take-home messages regarding pegvaliase therapy.

RESULTS

The panel discussed 18 cases, 11 males and 7 females (age range 17-43 years). At the last follow-up (up to 111 weeks after pegvaliase initiation), 11 out of 18 patients (61%) reached Phe levels below 600 μmol/l. Outcomes varied significantly across cases. All cases underscore the potential of pegvaliase in reducing Phe levels, enhancing the quality of life, and promoting social skills and independence. Additionally, the cases highlight the challenges associated with pegvaliase therapy, including managing adverse events and ensuring patient motivation and adherence.

CONCLUSION

This is the first report about the Italian experience of managing patients affected by PKU with pegvaliase. Given the limited real-world data on the use of pegvaliase in PKU management, this case series offers valuable insights into the practical implementation and management of pegvaliase therapy in this Country. Continued research and data collection will be crucial to confirm and progress with this treatment. Despite potential challenges, pegvaliase therapy represents a substantial promise in managing PKU in Italy. Patient education, personalized treatment approaches, and careful monitoring are important to ensure optimal patient outcomes.

Possible role of tryptophan metabolism along the microbiota-gut-brain axis on cognitive & behavioral aspects in Phenylketonuria

Cognitive and psychiatric disorders are well documented across the lifetime of patients with inborn errors of metabolism (IEMs). Gut microbiota impacts behavior and cognitive functions through the gut-brain axis (GBA). According to recent research, a broad spectrum of GBA disorders may be influenced by a perturbed Tryptophan (Trp) metabolism and are associated with alterations in composition or function of the gut microbiota. Furthermore, early-life diets may influence children's neurodevelopment and cognitive deficits in adulthood. In Phenylketonuria (PKU), since the main therapeutic intervention is based on a life-long restrictive diet, important alterations of gut microbiota have been observed. Studies on PKU highlight the impact of alterations of gut microbiota on the central nervous system (CNS), also investigating the involvement of metabolic pathways, such as Trp and kynurenine (KYN) metabolisms, involved in numerous neurodegenerative disorders. An alteration of Trp metabolism with an imbalance of the KYN pathway towards the production of neurotoxic metabolites implicated in numerous neurodegenerative and inflammatory diseases has been observed in PKU patients supplemented with Phe-free amino acid medical foods (AA-MF). The present review investigates the possible link between gut microbiota and the brain in IEMs, focusing on Trp metabolism in PKU. Considering the evidence collected, cognitive and behavioral well-being should always be monitored in routine IEMs clinical management. Further studies are required to evaluate the possible impact of Trp metabolism, through gut microbiota, on cognitive and behavioral functions in IEMs, to identify innovative dietetic strategies and improve quality of life and mental health of these patients.

Low bone mineralization in phenylketonuria may be due to undiagnosed metabolic acidosis

Background

Dietary intervention is to date the mainstay treatment to prevent toxic phenylalanine (Phe) accumulation in PKU patients. Despite success preventing central nervous system damage, there is increasing evidence of possible other unfavorable outcomes affecting other systems, e.g. kidney and bone; underlying mechanisms are yet to be fully elucidated.

Methods

This observational, cross-sectional and descriptive study investigated 20 adult with PKU evaluating biochemical parameters, BMD measurements and extrapolating data from 3-days food records and protein substitutes (PS) and special low protein foods (SLPF) composition.

Results

Blood gas venous analysis (VBG) indices were indicative of metabolic acidosis in 60% of PKU patients and VBG pH significantly correlated with BMD's Z-score (p-value = 0.022) even if its overall mean was in range (-1.29). Low bone mineral density for chronological age (Z-score < - 2.0) was found in 4 patients (20%). Indices of kidney function were not impaired. All used PS had a moderate excess of acidity, while SLPF were alkalizing and type/variety of consumed vegetables did not determine significant changes in acid-base equilibrium. Total intakes of potassium and magnesium were lower than expected.

Discussion

PKU patients seem to be at risk of metabolic acidosis, directly linked to possible low bone mineralization. This may be related to the acidic composition of PS, potentially capable of acidifying the entire diet. Reported low intakes of potassium and magnesium may be relevant to these observations. Further studies are needed to better address these topics.

Hyperphenylalaninemias genotyping: Results of over 60 years of history in Lombardy, Italy

BACKGROUND

Hyperphenylalaninemias (HPA) are due to several gene mutations, of which the PAH gene is the most frequently involved. Prevalence and incidence of disease vary between populations, with genotype/phenotype correlations not always capable to correctly predict disease severity. The aim of this study was to give an overview of PAH mutations among one of the largest cohort of patients among Europe, born in Lombardy (Italy) starting from late 1970 s and including over a 60 years of activity; furthermore, to evaluate and discuss identified genotype/phenotype correlations and related reliability.

PATIENTS/METHODS

Eight hundred and twenty-six HPA patients in current follow-up at the San Paolo Hospital in Milan (Italy) were retrospectively reviewed, including molecular results and allelic phenotype and genotype values (attributed on the basis of the APV/GPV system) to verify genotype-phenotype correlations.

RESULTS

A total of 166 different PAH variants were reviewed; of those, seven variants were identified as not previously described in literature. Most frequently reported variant was p.Ala403Val, followed by p.Arg261Gln, p.Val245Ala, IVS10-11 g>a, p.Tyr414Cys and p.Leu48Ser. Phenotype prediction, based on APV/GPV, matched the actual phenotype in most cases, but not always.

CONCLUSION/DISCUSSION

The cohort of patients included in this study constitute a representative sample of the HPA population worldwide. Studies on this sample may allow to improve clinical and genetic evaluation performances for affected patients, consequently to develop personalized medicine interventions and provide more precise indications on the correct treatment approach based on the accumulated evidence, also in light of a prognostically reliable but not always conclusive APV/GPV system.

Glycomacropeptide Safety and Its Effect on Gut Microbiota in Patients with Phenylketonuria: A Pilot Study

Glycomacropeptide (GMP) represents a good alternative protein source in Phenylketonuria (PKU). In a mouse model, it has been suggested to exert a prebiotic role on beneficial gut bacteria. In this study, we performed the 16S rRNA sequencing to evaluate the effect of 6 months of GMP supplementation on the gut microbiota of nine PKU patients, comparing their bacterial composition and clinical parameters before and after the intervention. GMP seems to be safe from both the microbiological and the clinical point of view. Indeed, we did not observe dramatic changes in the gut microbiota but a specific prebiotic effect on the butyrate-producer Agathobacter spp. and, to a lesser extent, of Subdoligranulum. Clinically, GMP intake did not show a significant impact on both metabolic control, as phenylalanine values were kept below the age target and nutritional parameters. On the other hand, an amelioration of calcium phosphate homeostasis was observed, with an increase in plasmatic vitamin D and a decrease in alkaline phosphatase. Our results suggest GMP as a safe alternative in the PKU diet and its possible prebiotic role on specific taxa without causing dramatic changes in the commensal microbiota.

L-alanine supplementation in Pompe disease (IOPD): a potential therapeutic implementation for patients on ERT? A case report

Background

Pompe disease (PD) is a disorder of glycogen metabolism conditioning a progressive and life conditioning myopathy. Enzyme replacement therapy (ERT) is currently the best treatment option for PD, but is not resolutive. While other potential therapeutic approaches have been reported before, these have never been tried as co- treatments. L-alanine oral supplementation (LAOS) has been proven to reduce muscle breakdown: we hereby report the first case of supplementation on a PD patient on ERT.

Case presentation

F. is a 9 y.o. infantile onset Pompe Disease (IOPD) girl ERT-treated since age 1 developing a progressive myopathy. We started her on LAOS and performed assessments at baseline, 6 and 9 months. At baseline, F.’s weight, height and BMI were within normal ranges, while body composition showed low fat mass -FM and high resting energy expenditure—REE levels. After LAOS, a progressive FM increase and REE reduction could be observed both at 6 and 9 months.

Conclusions

ERT is not curative for PD patients thus additional treatments could be considered to improve outcomes. Our patient showed physical signs of inability to accumulate energy when exclusively on ERT, while FM increase and REE reduction occurred when supplemented with LAOS, likely reflecting anabolic pathways’ implementation. This is the first case reporting potential LAOS benefits in PD-on ERT patients. Longitudinal case control studies are yet needed to evaluate possible efficacy of combined LAOS And ERT treatment in PD patients.

Italian national consensus statement on management and pharmacological treatment of phenylketonuria

BACKGROUND

Phenylketonuria (PKU) is a rare inherited metabolic disorder caused by defects in the phenylalanine-hydroxylase gene (PAH), the enzyme catalyzing the conversion of phenylalanine to tyrosine. PAH impairment causes phenylalanine accumulation in the blood and brain, with a broad spectrum of pathophysiological and neurological consequences for patients. Prevalence of disease varies, with peaks in some regions and countries, including Italy. A recent expert survey described the real-life of clinical practice for PKU in Italy, revealing inhomogeneities in disease management, particularly concerning approach to pharmacotherapy with sapropterin hydrochloride, analogous of the natural PAH co-factor, allowing disease control in a subset of patients. Therefore, the purpose of this paper is to continue the work initiated with the expert survey paper, to provide national guidances aiming to harmonize and optimize patient care at a national level.

PARTICIPANTS

The Consensus Group, convened by 10 Steering Committee members, consisted of a multidisciplinary crowd of 46 experts in the management of PKU in Italy.

CONSENSUS PROCESS

The Steering Committee met in a series of virtual meeting in order to discuss on clinical focuses to be developed and analyzed in guidance statements, on the basis of expert practice based evidence, large systematic literature review previously performed in the expert survey paper, and evidence based consensus published. Statements were re-discussed and refined during consensus conferences in the widest audience of experts, and finally submitted to the whole consensus group for a modified-Delphi voting.

RESULTS

Seventy three statements, divided in two main clinical areas, PKU management and Pharmacotherapy, achieved large consensus in a multidisciplinary group of expert in different aspects of disease. Importantly, these statements involve guidances for the use of sapropterin dihydrochloride, still not sufficiently implemented in Italy, and a set of good practice to approach the use of novel enzyme replacement treatment pegvaliase.

CONCLUSIONS

This evidence-based consensus provides a minimum set of guidances for disease management to be implemented in all PKU centers. Moreover, these guidances represent the first statement for sapropterin dihydrochloride use, implementation and standardization in Italy, and a guide for approaching pegvaliase treatment at a national level on a consistent basis.

Telehealth and COVID-19: Empowering Standards of Management for Patients Affected by Phenylketonuria and Hyperphenylalaninemia

Phenylketonuria (PKU) and Hyperphenylalaninemia (HPA) are inborn errors of metabolism (IEM) due to mutations in the PAH gene resulting in increased blood phenylalanine (Phe) concentrations. Depending on the Phe levels, a lifelong dietary intervention may be needed. During the COVID-19 pandemic, finding new strategies to ensure follow-up and metabolic control for such patients became mandatory and telehealth was identified as the most eligible tool to provide care and assistance beyond barriers. The aim of this study was to evaluate how telehealth use may have impacted disease follow-ups. Seven hundred and fifty-five patients affected by PKU/HPA in follow-ups at the Clinical Department of Pediatrics (San Paolo Hospital, ASST Santi Paolo e Carlo, University of Milan, Italy) were included in this study. The data regarding the used telehealth model, type of performed consultations and patients' perspectives were retrospectively collected and analyzed after a one-year experience of implemented follow-ups. The results demonstrated that telehealth seemed to be a useful tool to improve the adherence to treatment and that it could guarantee continuous assistance and care beyond the surrounding epidemiological status. Patients expressed great satisfaction with the offered services and requested that they were implemented in standards of care on a long-term basis. Our results suggested the implementation of telehealth in the management guidelines for PKU/HPA patients.

Dysbiosis, Host Metabolism, and Non-communicable Diseases: Trialogue in the Inborn Errors of Metabolism

Inborn errors of metabolism (IEMs) represent a complex system model, in need of a shift of approach exploring the main factors mediating the regulation of the system, internal or external and overcoming the traditional concept of biochemical and genetic defects. In this context, among the established factors influencing the metabolic flux, i.e., diet, lifestyle, antibiotics, xenobiotics, infectious agents, also the individual gut microbiota should be considered. A healthy gut microbiota contributes in maintaining human health by providing unique metabolic functions to the human host. Many patients with IEMs are on special diets, the main treatment for these diseases. Hence, IEMs represent a good model to evaluate how specific dietary patterns, in terms of macronutrients composition and quality of nutrients, can be related to a characteristic microbiota associated with a specific clinical phenotype (“enterophenotype”). In the present review, we aim at reporting the possible links existing between dysbiosis, a condition reported in IEMs patients, and a pro-inflammatory status, through an altered “gut-liver” cross-talk network and a major oxidative stress, with a repercussion on the health status of the patient, increasing the risk of non-communicable diseases (NCDs). On this basis, more attention should be paid to the nutritional status assessment and the clinical and biochemical signs of possible onset of comorbidities, with the goal of improving the long-term wellbeing in IEMs. A balanced intestinal ecosystem has been shown to positively contribute to patient health and its perturbation may influence the clinical spectrum of individuals with IEMs. For this, reaching eubiosis through the improvement of the quality of dietary products and mixtures, the use of pre-, pro- and postbiotics, could represent both a preventive and therapeutic strategy in these complex diseases.

PKU and COVID19: How the pandemic changed metabolic control

BACKGROUND

COVID19 pandemic urged the need to take severe measures for reducing the epidemic spread. Lockdowns were imposed throughout countries and even Inborn errors of metabolism (IEMs) affected patients had to face it and adapt, with management strategies changes coming along. Phenylketonuria (PKU) is an inborn error of phenylalanine (Phe) metabolism causing, when not treated, blood Phe increases and consequent central nervous system (CNS) damage. Dietary intervention is the main recognized treatment and must be maintained long-life, however adherence is often suboptimal in adulthood. Aim of this study was to evaluate whether and how the pandemic had impacted PKUs metabolic control and what factors may have played a role as potential modifiers.

METHODS

Patients ≥4 yo and in follow-up at our Metabolic Clinic were enrolled in this study, divided into subgroups according to age (GROUP A < 12 yo; GROUP B ≥ 12 yo). Videoconsults were conducted on a minimum monthly basis and collected DBS were studied and compared to previous year same time-period in order to evaluate possible changes.

RESULTS

39% of patients (n = 121) increased the number of performed DBS. "Non-compliant" patients were reduced (11-3%) with a - 14% of patients with mean Phe levels >600 umol/l and a - 8% of patients with 100% DBS above same level. GROUP A maintained substantially unchanged metabolic control among two analyzed time-periods. On the contrary, GROUP B demonstrated significant reductions in mean blood Phe concentrations (p < 0.0001) during the pandemic (mean 454 umol/l, SD ± 252, vs. 556.4 umol/l, SD ± 301).

DISCUSSION

COVID19 pandemic strongly impacted people's life with lifestyle habits changing consistently. PKU patients had to adapt their dietary restrictions to the new environment they were exposed to and, if younger patients could have been less exposed (meals strictly according to diet plan independently from setting), adolescent and adults strongly reflected the obligation to stay home by showing better metabolic control. Multiple factors could have played a role in that and the availability of teleconsultancy may have contributed allowing easier connections, but our data demonstrate how the pandemic and the environment can strongly impact PKUs adherence to treatment and how removing distance barriers can ameliorate and optimize metabolic compliance.

Weaning practices in phenylketonuria vary between health professionals in Europe

Background

In phenylketonuria (PKU), weaning is considered more challenging when compared to feeding healthy infants. The primary aim of weaning is to gradually replace natural protein from breast milk or standard infant formula with solids containing equivalent phenylalanine (Phe). In addition, a Phe-free second stage L-amino acid supplement is usually recommended from around 6 months to replace Phe-free infant formula. Our aim was to assess different weaning approaches used by health professionals across Europe.

Methods

A cross sectional questionnaire (survey monkey®) composed of 31 multiple and single choice questions was sent to European colleagues caring for inherited metabolic disorders (IMD). Centres were grouped into geographical regions for analysis.

Results

Weaning started at 17–26 weeks in 85% (n = 81/95) of centres, >26 weeks in 12% (n = 11/95) and < 17 weeks in 3% (n = 3/95). Infant's showing an interest in solid foods, and their age, were important determinant factors influencing weaning commencement. 51% (n = 48/95) of centres introduced Phe containing foods at 17–26 weeks and 48% (n = 46/95) at >26 weeks. First solids were mainly low Phe vegetables (59%, n = 56/95) and fruit (34%, n = 32/95).

A Phe exchange system to allocate dietary Phe was used by 52% (n = 49/95) of centres predominantly from Northern and Southern Europe and 48% (n = 46/95) calculated most Phe containing food sources (all centres in Eastern Europe and the majority from Germany and Austria). Some centres used a combination of both methods.

A second stage Phe-free L-amino acid supplement containing a higher protein equivalent was introduced by 41% (n = 39/95) of centres at infant age 26–36 weeks (mainly from Germany, Austria, Northern and Eastern Europe) and 37% (n = 35/95) at infant age > 1y mainly from Southern Europe. 53% (n = 50/95) of centres recommended a second stage Phe-free L-amino acid supplement in a spoonable or semi-solid form.

Conclusions

Weaning strategies vary throughout European PKU centres. There is evidence to suggest that different infant weaning strategies may influence longer term adherence to the PKU diet or acceptance of Phe-free L-amino acid supplements; rendering prospective long-term studies important. It is essential to identify an effective weaning strategy that reduces caregiver burden but is associated with acceptable dietary adherence and optimal infant feeding development.

Early feeding practices in infants with phenylketonuria across Europe

Background

In infants with phenylketonuria (PKU), dietary management is based on lowering and titrating phenylalanine (Phe) intake from breast milk or standard infant formula in combination with a Phe-free infant formula in order to maintain blood Phe levels within target range. Professionals use different methods to feed infants with PKU and our survey aimed to document practices across Europe.

Methods

We sent a cross sectional, survey monkey® questionnaire to European health professionals working in IMD. It contained 31 open and multiple-choice questions. The results were analysed according to different geographical regions.

Results

Ninety-five centres from 21 countries responded. Over 60% of centres commenced diet in infants by age 10 days, with 58% of centres implementing newborn screening by day 3 post birth. At diagnosis, infant hospital admission occurred in 61% of metabolic centres, mainly in Eastern, Western and Southern Europe. Breastfeeding fell sharply following diagnosis with only 30% of women still breast feeding at 6 months.

53% of centres gave pre-measured Phe-free infant formula before each breast feed and 23% alternated breast feeds with Phe-free infant formula. With standard infant formula feeds, measured amounts were followed by Phe-free infant formula to satiety in 37% of centres (n = 35/95), whereas 44% (n = 42/95) advised mixing both formulas together. Weaning commenced between 17 and 26 weeks in 85% centres, ≥26 weeks in 12% and < 17 weeks in 3%.

Discussion

This is the largest European survey completed on PKU infant feeding practices. It is evident that practices varied widely across Europe, and the practicalities of infant feeding in PKU received little focus in the PKU European Guidelines (2017). There are few reports comparing different feeding techniques with blood Phe control, Phe fluctuations and growth. Controlled prospective studies are necessary to assess how different infant feeding practices may influence longer term feeding development.