Homogentisic acid is not only eliminated by glomerular filtration and tubular secretion but also produced in the kidney in alkaptonuria.

The clinical effects of alkaptonuria (AKU) are delayed and ageing influences disease progression. Morbidity of AKU is secondary to high circulating homogentisic acid (HGA) and ochronosis. It is not known whether HGA is produced by or processed in the kidney in AKU. Data from AKU patients from four studies were merged to form a single AKU group. A control group of non-AKU subjects was generated by merging data from two non-AKU studies. Data were used to derive renal clearance and fractional excretion (FE) ratios for creatinine, HGA, phenylalanine (PHE) and tyrosine (TYR) using standard calculations, for comparison between the AKU and the control groups. There were 225 AKU patients in the AKU group and 52 in the non-AKU control group. Circulating HGA increased with age (P < 0.001), and was significantly associated with decreased HGA clearance (CLHGA ) (P < 0.001) and FEHGA (P < 0.001). CLHGA and FEHGA were increased beyond the theoretical maximum renal plasma flow, confirming renal production and emphasising the greater contribution of net tubular secretion than glomerular filtration to renal elimination of HGA. The kidneys are crucial to elimination of HGA. Elimination of HGA is impaired with age resulting in worsening disease over time. The kidney is an important site for production of HGA. Tubular secretion of HGA contributes more to elimination of HGA in AKU than glomerular filtration.

Alkaptonuria: An example of a "fundamental disease"--A rare disease with important lessons for more common disorders.

"Fundamental diseases" is a term introduced by the charity Findacure to describe rare genetic disorders that are gateways to understanding common conditions and human physiology. The concept that rare diseases have important lessons for biomedical science has been recognised by some of the great figures in the history of medical research, including Harvey, Bateson and Garrod. Here we describe some of the recently discovered lessons from the study of the iconic genetic disease alkaptonuria (AKU), which have shed new light on understanding the pathogenesis of osteoarthritis. In AKU, ochronotic pigment is deposited in cartilage when collagen fibrils become susceptible to attack by homogentisic acid (HGA). When HGA binds to collagen, cartilage matrix becomes stiffened, resulting in the aberrant transmission of loading to underlying subchondral bone. Aberrant loading leads to the formation of pathophysiological structures including trabecular excrescences and high density mineralised protrusions (HDMPs). These structures initially identified in AKU have subsequently been found in more common osteoarthritis and appear to play a role in joint destruction in both diseases.

Suitability Of Nitisinone In Alkaptonuria 1 (SONIA 1): an international, multicentre, randomised, open-label, no-treatment controlled, parallel-group, dose-response study to investigate the effect of once daily nitisinone on 24-h urinary homogentisic acid excretion in patients with alkaptonuria after 4 weeks of treatment.

BACKGROUND: Alkaptonuria (AKU) is a serious genetic disease characterised by premature spondyloarthropathy. Homogentisate-lowering therapy is being investigated for AKU. Nitisinone decreases homogentisic acid (HGA) in AKU but the dose-response relationship has not been previously studied. METHODS: Suitability Of Nitisinone In Alkaptonuria 1 (SONIA 1) was an international, multicentre, randomised, open-label, no-treatment controlled, parallel-group, dose-response study. The primary objective was to investigate the effect of different doses of nitisinone once daily on 24-h urinary HGA excretion (u-HGA24) in patients with AKU after 4 weeks of treatment. Forty patients were randomised into five groups of eight patients each, with groups receiving no treatment or 1 mg, 2 mg, 4 mg and 8 mg of nitisinone. FINDINGS: A clear dose-response relationship was observed between nitisinone and the urinary excretion of HGA. At 4 weeks, the adjusted geometric mean u-HGA24 was 31.53 mmol, 3.26 mmol, 1.44 mmol, 0.57 mmol and 0.15 mmol for the no treatment or 1 mg, 2 mg, 4 mg and 8 mg doses, respectively. For the most efficacious dose, 8 mg daily, this corresponds to a mean reduction of u-HGA24 of 98.8% compared with baseline. An increase in tyrosine levels was seen at all doses but the dose-response relationship was less clear than the effect on HGA. Despite tyrosinaemia, there were no safety concerns and no serious adverse events were reported over the 4 weeks of nitisinone therapy. CONCLUSIONS: In this study in patients with AKU, nitisinone therapy decreased urinary HGA excretion to low levels in a dose-dependent manner and was well tolerated within the studied dose range. TRIAL REGISTRATION NUMBER: EudraCT number: 2012-005340-24. Registered at ClinicalTrials.gov: NCTO1828463.

Old treatments for new insights and strategies: proposed management in adults and children with alkaptonuria.

Alkaptonuria (AKU) is caused by deficiency of the enzyme homogentisate 1,2 dioxygenase. It results in an accumulation of homogentisate which oxidizes spontaneously to benzoquinone acetate, a highly oxidant compound, which polymerises to a melanin-like structure, in a process called ochronosis. Asymptomatic during childhood, this accumulation will lead from the second decade of life to a progressive and severe spondylo-arthopathy, associated with multisystem involvement: osteoporosis/fractures, stones (renal, prostatic, gall bladder, salivary glands), ruptures of tendons/muscle/ligaments, renal failure and aortic valve disease. The pathophysiological mechanisms of AKU remain poorly understood, but recent advances lead us to reconsider the treatment strategy in AKU patients. Besides the supporting therapies (pain killers, anti-inflammatory drugs, physiotherapy, joints replacements and others), specific therapies have been considered (anti-oxidant, low protein diet, nitisinone), but clinical studies have failed to prove efficiency on the rheumatological lesions of the disease. Here we propose a treatment strategy for children and adults with AKU, based on a review of the latest findings on AKU and lessons from other aminoacipathies, especially tyrosinemias.

Comparing nitisinone 2 mg and 10 mg in the treatment of alkaptonuria-An approach using statistical modelling.

BACKGROUND: Outcomes from studies employing nitisinone 10 mg and 2 mg in alkaptonuria were compared. PATIENTS AND METHODS: Sixty-nine patients in each of the nitisinone (10 mg daily) and controls of suitability of nitisinone in alkaptonuria 2 (SONIA 2), as well as 37 and 23 in nitisinone (2 mg daily) and control cohorts at the National Alkaptonuria Centre (NAC), respectively, were followed up for 4 years. Severity of alkaptonuria (AKU) was assessed by the AKU Severity Score Index (AKUSSI). 24-h urine homogentisic acid (uHGA24), serum HGA (sHGA), serum tyrosine (sTYR) and serum nitisinone (sNIT) were also analysed at each time point. Dietetic support was used in the NAC, but not in SONIA 2. Safety outcomes were also compared. All statistical analyses were post hoc. RESULTS: The slope of the AKUSSI was 0.55, 0.19, 0.30, and 0.06 per month in the control NAC, nitisinone NAC, control SONIA 2, and nitisinone SONIA 2 cohorts, respectively. The intersection of the slopes on the x-axis was -132, -411, -295, and - 1460 months, respectively. The control and nitisinone slope comparisons were statistically significant both in the NAC (p < 0.001) and the SONIA 2 (p < 0.001). Corneal keratopathy occurred in 3 and 10 patients in the NAC and SONIA 2, respectively. DISCUSSION: The nitisinone 10 mg dose decreased disease progression more than the 2 mg dose although the incidence of corneal keratopathy was 14.5% and 4.9%, respectively. CONCLUSION: Nitisinone 10 mg decreased urine and serum HGA, increased serum tyrosine, and decreased disease progression more than 2 mg. Low-protein dietetic support may be needed to mitigate tyrosinaemia following nitisinone. HIGHLIGHTS: Nitisinone 10 mg apparently slows alkaptonuria disease progression more than 2 mg in adults.Corneal keratopathy during nitisinone therapy was more common in men.Serum nitisinone concentrations increased significantly over time.Nitisinone may inhibit cytochrome P450 self catabolism.

Identifying obstacles hindering the conduct of academic-sponsored trials for drug repurposing on rare-diseases: an analysis of six use cases.

BACKGROUND: Academic-sponsored trials for rare diseases face many challenges; the present paper identifies hurdles in the set-up of six multinational clinical trials for drug repurposing, as use cases. METHODS: Six academic-sponsored multinational trials aiming to generate knowledge on rare diseases drug repurposing were used as examples to identify problems in their set-up. Coordinating investigators leading these trials provided feedback on hurdles linked to study, country, and site set up, on the basis of pre-identified categories established through the analysis of previous peer-reviewed publications. RESULTS: Administrative burden and lack of harmonization for trial-site agreements were deemed as a major hurdle. Other main identified obstacles included the following: (1) complexity and restriction on the use of public funding, especially in a multinational set up, (2) drug supply, including procurement tendering rules and country-specific requirements for drug stability, and (3) lack of harmonization on regulatory requirements to get trial approvals. CONCLUSION: A better knowledge of the non-commercial clinical research landscape and its challenges and requirements is needed to make drugs-especially those with less commercial gain-accessible to rare diseases patients. Better information about existing resources like research infrastructures, clinical research programs, and counseling mechanisms is needed to support and guide clinicians through the many challenges associated to the set-up of academic-sponsored multinational trials.

Clinical development innovation in rare diseases: lessons learned and best practices from the DevelopAKUre consortium.

New opportunities have arisen for development of therapies for rare diseases with the increased focus and progress in the field. However, standardised framework integrating individual initiatives has not been formed. We present lessons learned and best practice from a collaborative success case in developing a treatment for a rare genetic disease. Our unique consortium model incorporated several of the identified developments under one project, DevelopAKUre, truly bringing together academia, industry and patient organisations in clinical drug development. We found that the equal partnership between all parties in our consortium was a key success factor creating a momentum based on a strong organisational culture where all partners had high engagement and taking ownership of the entire programme. With an agreed mutual objective, this provided synergies through connecting the strengths of the individual parties. Another key success factor was the central role of the patient organisation within the management team, and their unique study participants' advocacy role securing the understanding and meeting the needs of the clinical study participants in real-time. This resulted in an accelerated enrolment into the clinical studies with a high retention rate allowing for delivery of the programme with significantly improved timelines. Our project was partly funded through an external EU research grant, enabling our model with equal partnership. Further attention within the community should be given to establishing a functional framework where sustainable funding and risk sharing between private and public organisations allow for our model to be replicated.

A patient survey on the impact of alkaptonuria symptoms as perceived by the patients and their experiences of receiving diagnosis and care.

BACKGROUND: Alkaptonuria (AKU) is an ultrarare and multifaceted disease characterized by the absence of functional homogentisate 1,2-dioxygenase activity, the enzyme responsible for breakdown of homogentisic acid-a tyrosine-degradation product. The presymptomatic phase of the disease makes diagnosis difficult, with many patients unidentified or diagnosed late in life. OBJECTIVE: To date, no study has analyzed the perceived impact of different symptoms or the experiences of individuals through the patient journey in the context of AKU. This study aimed to examine patients' perceptions of AKU symptoms and their impact on quality of life as well as patients' experiences of being diagnosed and living with the disease. METHODS: Data for this study were collected using a quantitative self-report questionnaire administered online to people with AKU. RESULTS: Data from 45 participants indicate that symptoms with the highest impact for patients are those related to pain and ruptures, disability and inability to perform normal routines, emotional/mental health issues, and heart complications. Findings also revealed significant delays in contact with healthcare services and time to diagnosis. Furthermore, patients reported difficulty in receiving information about AKU, treatment and care, and long-term disease management support. CONCLUSIONS: Time to diagnosis and care of AKU is significantly delayed. Symptoms of AKU with the highest impact on quality of life for patients are those related to pain and disability and the inability to perform normal routines. Bridging any gaps between patients with AKU and healthcare professionals through education could help improve patients' experiences with AKU through the patient journey.

Efficacy and safety of once-daily nitisinone for patients with alkaptonuria (SONIA 2): an international, multicentre, open-label, randomised controlled trial.

BACKGROUND: Alkaptonuria is a rare, genetic, multisystem disease characterised by the accumulation of homogentisic acid (HGA). No HGA-lowering therapy has been approved to date. The aim of SONIA 2 was to investigate the efficacy and safety of once-daily nitisinone for reducing HGA excretion in patients with alkaptonuria and to evaluate whether nitisinone has a clinical benefit. METHODS: SONIA 2 was a 4-year, open-label, evaluator-blind, randomised, no treatment controlled, parallel-group study done at three sites in the UK, France, and Slovakia. Patients aged 25 years or older with confirmed alkaptonuria and any clinical disease manifestations were randomly assigned (1:1) to receive either oral nitisinone 10 mg daily or no treatment. Patients could not be masked to treatment due to colour changes in the urine, but the study was evaluator-blinded as far as possible. The primary endpoint was daily urinary HGA excretion (u-HGA24) after 12 months. Clinical evaluation Alkaptonuria Severity Score Index (cAKUSSI) score was assessed at 12, 24, 36, and 48 months. Efficacy variables were analysed in all randomly assigned patients with a valid u-HGA24 measurement at baseline. Safety variables were analysed in all randomly assigned patients. The study was registered at ClinicalTrials.gov (NCT01916382). FINDINGS: Between May 7, 2014, and Feb 16, 2015, 139 patients were screened, of whom 138 were included in the study, with 69 patients randomly assigned to each group. 55 patients in the nitisinone group and 53 in the control group completed the study. u-HGA24 at 12 months was significantly decreased by 99·7% in the nitisinone group compared with the control group (adjusted geometric mean ratio of nitisinone/control 0·003 [95% CI 0·003 to 0·004], p<0·0001). At 48 months, the increase in cAKUSSI score from baseline was significantly lower in the nitisinone group compared with the control group (adjusted mean difference -8·6 points [-16·0 to -1·2], p=0·023). 400 adverse events occurred in 59 (86%) patients in the nitisinone group and 284 events occurred in 57 (83%) patients in the control group. No treatment-related deaths occurred. INTERPRETATION: Nitisinone 10 mg daily was well tolerated and effective in reducing urinary excretion of HGA. Nitisinone decreased ochronosis and improved clinical signs, indicating a slower disease progression. FUNDING: European Commission Seventh Framework Programme.

Twelve novel HGD gene variants identified in 99 alkaptonuria patients: focus on 'black bone disease' in Italy.

Alkaptonuria (AKU) is an autosomal recessive disorder caused by mutations in homogentisate-1,2-dioxygenase (HGD) gene leading to the deficiency of HGD enzyme activity. The DevelopAKUre project is underway to test nitisinone as a specific treatment to counteract this derangement of the phenylalanine-tyrosine catabolic pathway. We analysed DNA of 40 AKU patients enrolled for SONIA1, the first study in DevelopAKUre, and of 59 other AKU patients sent to our laboratory for molecular diagnostics. We identified 12 novel DNA variants: one was identified in patients from Brazil (c.557T>A), Slovakia (c.500C>T) and France (c.440T>C), three in patients from India (c.469+6T>C, c.650-85A>G, c.158G>A), and six in patients from Italy (c.742A>G, c.614G>A, c.1057A>C, c.752G>A, c.119A>C, c.926G>T). Thus, the total number of potential AKU-causing variants found in 380 patients reported in the HGD mutation database is now 129. Using mCSM and DUET, computational approaches based on the protein 3D structure, the novel missense variants are predicted to affect the activity of the enzyme by three mechanisms: decrease of stability of individual protomers, disruption of protomer-protomer interactions or modification of residues in the region of the active site. We also present an overview of AKU in Italy, where so far about 60 AKU cases are known and DNA analysis has been reported for 34 of them. In this rather small group, 26 different HGD variants affecting function were described, indicating rather high heterogeneity. Twelve of these variants seem to be specific for Italy.