Advances in UCD treatment and management of UCDs

Transcription

1 Advances in UCD treatment and management of UCDs Brendan Lee M.D.,Ph.D. Howard Hughes Medical Institute Department of Molecular and Human Genetics Baylor College of Medicine

2 Nitrogen and the urea cycle Food Ammonia Urea Breakdown of body proteins (stress)

3

4 Why a cycle Four synthetic steps and two degradative steps to transfer one nitrogen from ammonia and one nitrogen from aspartate to the two nitrogens in urea Ornithine is always regenerated No net synthesis or production of urea cycle intermediates Mitochondrial and plasma membrane transporters important

5 Why a urea cycle Eliminate 40-45% of food protein nitrogen that is not needed for growth Provide important intermediates for other biochemical pathways (Arginine) Net synthesis of intermediates from the gut and kidneys

6 Pathogenesis of UCDs Carbamyl Phosphate + Ornithine X Citrulline X X X AMMONIA Arginine X Argininosuccinic Acid

7 Urea Cycle Disorders: Treatment Food Restrict Protein intake Buphenyl Ammonul Benzoate Ammonia Urea Breakdown of body proteins (stress) Arginine Citrulline

8 Alternative route disposal of nitrogen Sodium Phenylbutyrate X UREA CYCLE Phenylacetate + Glutamine Glycine + Benzoate Phenylacetylglutamine Hippurate URINARY EXCRETION

9 Arginine/Citrulline Supplementation Carbamyl Phosphate + Ornithine X Citrulline X X X ASPARTATE AMMONIA Arginine X Argininosuccinic Acid

10 What is difficult to manage? Frequent hyperammonemia Treatment non-adherence Dietary protein restriction Medication intolerance Feeding aversion Poor growth and development

11 Case One Referral for difficult management 3 year old female diagnosed with partial OTCD by DNA Presented with recurrent vomiting Multiple GI evaluations Treated with protein restriction, Buphenyl, citrulline, carnitine Repeated hospitalizations 1-3/month (NH 3 < 200 µm) Feeding aversion; complex feeding regimen

12 AMINO ACID CONC 0-1 YR 2-18 YR (um) RANGE RANGE o-phosphoserine o-phosphoethanolamine Taurine Aspartic Acid Threonine Serine Asparagine Glutamic Acid Glutamine Proline Glycine Alanine Citrulline Amino-n-butyric Acid Argininosuccinic Acid Valine Cystine Methionine Isoleucine Leucine Tyrosine Phenylalanine Homocystine (free) 0 < 1 < 1 Ornithine Tryptophan Lysine l-methylhistidine Histidine Methylhistidine Arginine Albumin 4.1 g/dl ( ) Prealbumin 20 mg/dl (18 44)

13 AMINO ACID CONC 0-1 YR 2-18 YR (um) RANGE RANGE o-phosphoserine o-phosphoethanolamine Taurine Aspartic Acid Threonine Serine Asparagine Glutamic Acid Glutamine Proline Glycine Alanine Citrulline Amino-n-butyric Acid Argininosuccinic Acid Valine Cystine Methionine Isoleucine Leucine Tyrosine Phenylalanine Homocystine (free) 0 < 1 < 1 Ornithine Tryptophan Lysine l-methylhistidine Histidine Methylhistidine Arginine

14 Natural history of UCDs Infancy Childhood Adolescence Adulthood Growth rate Protein tolerance Susceptibility to hyperammonemia Development Spasticity, liver dysfunction, hypertension

15 Natural History Honeymoon period in early infancy Difficulties with control at the end of the first year and during rapid growth (puberty) More severe with NAGS, CPS, OTC null activity patients Increased protein tolerance with age Emerging correlations

16 The honeymoon period Rapid growth and protein utilization Restricted environmental exposures Simpler dietary regimens Environmental Switch from breast milk Introduction of solid foods Exposure to infectious agents

17 Pathogenesis Hyperammonemia Hyperglutaminemia? Elevated arginine in argininemia Elevated argininosuccinic acid in ASA Arginine deficiency Overzealous protein restriction Branched chain amino acid depletion Unique enzyme functions?

18 Catabolic stress vs. dietary nonadherence Magnitude of nitrogen utilization from peripheral vs. central sources Getting sick is worse then eating too much Eating too little is worse then eating too much Prevention of catabolic stress Clinical and subclinical infection Strenuous and prolonged exercise Feeding aversion and G-button

19 Effects of pharmacologic therapy β-oxidation rate Gastrointestinal effects Metabolic effects Arginine, citrulline, carbamylglutamate, citric acid, carnitine

20 Essential Amino Acids Branched Chain Amino Acids Leucine, Valine, Isoleucine Phenylalanine Lysine Methionine Threonine Tryptophan

21

22

23 Buphenyl Benzoate

24 Branched Chain Amino Acids and UCDs UCD patients treated with protein restriction and PB have low BCAAs in the face of protein sufficiency Control subjects given PAB have selective decrease of BCAAs Supplementation with BCAAs may enable better titration of protein restriction How does BCAA flux affect protein synthesis and nitrogen transfer in UCD?

25 BCAA supplementation in UCD Compare BCAA with other essential amino acids and other parameters of protein sufficiency vs. insufficiency Tolerance of protein restriction with BCAA supplementation? BCAA and Buphenyl for better management and/or decrease risk of catabolism?

26 Management of Urea Cycle Disorders: Rationale for Nutritional Support Restrict dietary protein Prevent total body protein catabolism Use essential AA mix to provide 50% protein prescription Mix of essential amino acids, protein-free formula, and cow s milk formula Supplement with BCAA to allow further titration of protein restriction

27 Laboratory evaluation Useful laboratories in the clinic visit Useful laboratories in the hospitalization Diurnal variation Evaluation at steady state

28 Currency of nitrogen transfer Sources Breakdown of dietary protein Breakdown of endogenous protein Glutamine Alanine Glycine Essential amino acids Ammonia

29

30 Psychosocial factors Access to healthcare Laboratory studies Dietary services Metabolic expertise Family participation Educational background

31 Caveats of treatment Stoichiometric conversion of medications G-button GI side effects Strict control of caloric and protein intake Growth requires essential amino acids

32 Long Term Correction of Urea Cycle Disorders Role for liver transplantation OTCD CPS ASL Gene replacement therapy

33 Liver Transplantation for UCDs Neonatal onset CPS, OTC Cirrhosis associated with ASL Difficult medical management (ASS?) Risk - benefit assessment Access to medical/surgical expertise Outcome Psycho-socioeconomic factors Risks of hyperammonemia vs. risks of surgery and immunosuppression

34 UNOS Transplant Registry January 1988 January patients with UCDs underwent OLT Type of liver 63% received cadveric whole livers 19% received cadaveric partial/reduced livers 12% received cadaveric split livers 6% received living related donor livers 5 year post-olt survival was 85% for UCD subtypes Overall retransplantation rate 7%

35

36 Table 2. Griffiths Developmental Scale Results Subj Visit Age (mo) Overall* Gross Motor Personal- Social Lang. Fine Motor Perf. Pract. Reas mo CPS mo OTC mo CPS DECEASED mo OTC * developmental scale results are standardized ratios, where mean =100, standard deviation =

37

38 Nitric oxide and the urea cycle Ornithine ArgI Arginine ASL NOS Citrulline + Nitric Oxide Argininosuccinic Acid

39 Nitrogen transfer through the urea cycle Diet (0.4 gm/kg/d protein) +/- Medication Day 1 Day 2 Day 3 CBC NH 3 PAA Infusion:[ 15 N]Gln & [ 18 O][ 13 C]Urea 0h 4h 8h 12h Measure NH 3, PAA [ 15 N]Gln [ 15 N]Urea [ 18 O]Urea

40

41

42

43 Acknowledgements Baylor College of Medicine Susan Carter R.N., Alyssa Tran, Brendan Lanpher, M.D., Fernando Scaglia, M.D., Nicola Brunetti, M.D.,Ph.D. Farook Jahoor, Ph.D., Juan Marini, Ph.D., Peter Garlick, Ph.D., William O Brien, Ph.D. GCRC, MRDRC, DDC UCD RDCRC NIH NIDDKD, NICHD Ucyclyd Pharma O Malley Foundation NUCDF and families

44 Helper-Dependent Adenoviral Vector Gene Therapy Reduction in chronic hepatic toxicity and adaptive immune response Increased duration of transgene expression Increased capacity for genomic DNA and tissue-specific genomic promoters and enhancers Increased capacity for multiple transgenes and regulatory switches

45 Urinary Orotic Acid (mm/mol creatinine) PBS PEPCK hotc PEPCK hotc-wpre Human OTC cdna PEPCK promoter LITR+Ψ * * * * * * * * * Weeks After Treatment WPRE RITR+E4 A. Mian et. al. Molecular Therapy 2004

46 Increased histochemical liver OTC activity in treated mice Wildtype Saline HDV-hOTC HDV-hOTC- WPRE 5 weeks 25 weeks A. Mian et. al. Molecular Therapy 2004

47 Dose response: Increasing the expression of hotc and effects on urinary orotic acid 5X10 11 vp/kg 1X10 12 vp/kg PEPCK hotc WPRE vs. PEPCK hotc WPRE HCR Nicola Brunetti

48 FG vs HD-Ad time course: Platelets Dose: 2 x vp/kg Each time point represents a group of 5 mice Viraj Mane

49 Reduced Thrombocytopenia in TNFα Null Mice * * * * Viraj Mane

50 Effects of TNFα Ab pretreatment * Viraj Mane

51 Efficiency of Ad-Mediated Hepatic Transduction Following Systemic Injection Nunes et al., 1999 Portal vein injection into rhesus Morral et al., 2001 Peripheral vein injection into baboon Brunetti-Pierri et al Peripheral vein injection into baboon 1 x x x x x x x x Conclusions: Dose (vp/kg) % transduction 1x % 5x x10 12 ~ 50% <<1% 5x10 11 undetectable Lethal human dose = 6x10 11 vp/kg

52 Dose response: Hydrodynamic expression of HDV Ad hotc and effects on urinary orotic acid mmol/mol Cr x10e12 conv 5x10e11 conv 5x10e11 Hydro 1x10e11 Hydro weeks after injection Doses in vp/kg Conv = conventional injection Hydro = hydrodynamic injection Nicola Brunetti

53 Phil Ng

54 Acute toxicity current approaches Threshold effect Local delivery and recirculation Saturation of nonspecific targets Increased gene expression Innate immune response Pegylation Pharmacologic blockade TNFα, complement, antibody

55 Acknowledgements William McCormack Gabriele Toietta Asad Mian Vincenzo Cerullo Viraj Mane Mike Seiler Nicola Brunetti Philip Ng Arthur Beaudet Jose Lopez Milton Finegold Lucio Pastore Lali K. Medine-Kauwe Timothy Nichols Anthony McDonagh Steven Pipe NIH NIDDKD, NICHD, BCM MRDDRC