Presentation on theme: "Kuvan ® the first drug treatment for PKU Peter Galloway Adult Metabolic Clinic Glasgow Royal Infirmary March 2010."— Presentation transcript:
Kuvan ® the first drug treatment for PKU Peter Galloway Adult Metabolic Clinic Glasgow Royal Infirmary March 2010
Chart plotting median PHE level for all patients diagnosed with PKU with any data since 2001 Average male PHE value Average female PHE value Upper recommended PHE limit Lower recommended PHE limit 45% control their PHE levels to within current guidelines (42% for males, 47% for females)
Chart plotting median lowest PHE level for all patients diagnosed with PKU with any data since 2001 Average lowest male PHE value Average lowest female PHE value Upper recommended PHE limit Lower recommended PHE limit
Phenylalanine ammonia lyase An enzyme found widely in yeasts and red-purple coloured plants and used in the synthesis of anthocyanins. It breaks down phenylalanine to hydrocinnamic acid Can be extracted from plants or synthesised by engineered E. coli bacteria Could be used to break down phenylalanine in the intestine, preventing its absorption and allowing liberalisation of the diet Easily destroyed by gastric acid and attempts to engineer a robust protected source of PAL have been abortive over more than 15 years….. Recently subcutaneous injection of pegylated enzyme has been successful in a mouse model of PKU First human trials involving 25 individuals in 2009
Tetrahydrobiopterin First reported 1963 by Kaufmann –Proc. National Academy of Science, 1968: 5: and first suggested role in –Journal of Biological Chemistry, 1975, 25:
In 1999 Kure reported 4 of 5 mild PKU, BH4 loading produced reductions in blood phenylalanine Journal of Paediatrics, 1999: 135:
Availability April 2009 – Launch of Kuvan Sapropterin licensed for use in Phenylketonuria in those over 4 years of age for the treatment of hyperphenylalaninaemia who have been shown to be responsive to such treatment.
Info: How is Kuvan taken? Dose? 5-20 mg/kg body weight 100 mg tablets Dissolved in water and taken one per day 8 year old may need 1-4 tablets/day Adult male may need 7-14 tablets/day
Possible Mechanisms for the BH4-Responsiveness K m mutants with reduced affinity for BH4 Chaperon-like activity of BH4 Induction of PAH expression by BH4 PAH mRNA stabilization Better assembly/stabilisation Possible Mechanisms for failure to respond Truncated protein Missing BH4 Binding Area
Tetrahydrobiopterin Loading Test in Patients with Hyperphenylalaninemia 20 mg/kg (BH4) Hours 20 mg/kg 10 mg/kg Blood Phenylalanine ( mol/L) PKU responder PKU non-responder BH4 def.
Burton et al PKU 001
Patients in PKU-003
PKU-003 Absolute phenylalanine before and after BH 4
PKU-003 Change in phenylalanine with BH 4
WHAT IS A RESPONSE > 30% reduction in phenylalanine While remaining on a constant protein intake Also need to be able to take an increased protein intake How long to show you respond?
Levy et al: test with BH 4 10mg/kg/day for up to 28 days
Blau N: Guidelines for the definition of BH4 responsiveness should include the following investigations…... Single loading test with 20 mg/kg BH 4 and monitoring of phe at 0,8,12,(15?) and 24 hours Reduction of phe of over 20-30% an indicator for a trial of BH 4 at initial doses of 10mg/kg/day over several weeks Titration of the individual BH4 requirement (5-20mg/kg/day)to maintain optimal phe levels Determination of the daily phenylalanine tolerance Genotyping
KUVAN Does it have other benefits than just reduction in levels? Not formally tested. Anecdotally – what does this mean?
Side-effects from Kuvan % Diarrhoea 5 Abdominal pain 5 Nausea 3 Flatulence2 Vomiting2 Decreased appetite2 Headache10 Fatigue3 Tremor 2 4 in 489 had severe SEs – migraine, headache, vomiting and low platelet count No patient discontinued the study from side-effects.
Why not give to everyone? Small proportion benefit – 1 in 5 30% reduction; 1 in 20 major dietary change Testing will be over a month – if dont respond effect ? Could start based on genetic testing. Cost
Other Issues Age it should be started? How long should it be continued? e.g. Childhood/end of schooling Lifelong If difficult complying with low protein diet, –? compliance with tablets. Monitoring while on treatment Other areas – pregnancy?
Current Progress - Where is Europe? Where is UK? What do you feel we should be doing?