INHEPP: Effect of Isoniazid on Protoporphyrin Levels in Erythropoietic Protoporphyria
Study Details
Study Description
Brief Summary
In erythropoietic protoporphyria there is an accumulation of protoporphyrin IX (PPIX) in the plasma and liver. The reason it builds up is either the last step to make heme, insertion of iron into PPIX, is rate limiting or there is an increase in activity in the first step in the heme pathway.
It may be possible to decrease the amount of PPIX made and see a decrease in symptoms. The first step to make heme is the key step in the pathway and it uses vitamin B6 as a cofactor. If the investigators can limit the amount of vitamin B6 the investigators can possibly reduce the activity of this rate limiting step. With decreased activity of the enzyme it may be possible for the body to utilize all the PPIX that is made so that none builds up.
| Condition or Disease | Intervention/Treatment | Phase |
|---|---|---|
| N/A |
Detailed Description
Clinically, both erythropoietic protoporphyria (EPP) and X-linked EPP (XLEPP) are characterized by painful, non-blistering cutaneous photosensitivity with onset in early childhood. EPP is the most common porphyria in children and the third most common in adults (after porphyria cutanea tarda and acute intermittent porphyria). Reports of prevalence vary between 5 and 15 cases per million population.
EPP is due in most cases to decreased activity of ferrochelatase (FECH), the enzyme that catalyzes the incorporation of ferrous iron into PPIX, the final step in the production of heme. The pattern of inheritance is autosomal recessive. However, homozygosity for a FECH mutation is rare. Rather, the decreased activity is a consequence of a combination of an inherited inactivating mutation affecting one FECH allele and an intronic polymorphism that alters splicing of the other allele. The alternative splice site, when used, produces a non-functional FECH messenger ribonucleic acid (mRNA). The alternative splice site is used approximately 40% of the time. Therefore, the polymorphic allele produces approximately 60% of normal FECH activity, and for this reason, is termed hypomorphic. When the hypomorphic FECH allele is in trans with the non-functional mutant allele the result is 30% or less of the normal FECH enzyme activity. This subnormal FECH activity becomes rate-limiting, resulting in accumulation of intracellular PPIX. Although the defect is presumably expressed in all tissues, the PPIX responsible for photosensitivity derives primarily from marrow reticulocytes.
Aminolevulinic acid synthase (ALAS), the first, and rate-limiting enzyme in the heme biosynthetic pathway, catalyzes the condensation of glycine and succinyl-Coenzyme A (succinyl-CoA) to form aminolevulinic acid (ALA), and requires pyridoxal 5'-phosphate as a cofactor. ALAS in mammalian cells is localized to the mitochondrial matrix. The enzyme is synthesized as a precursor protein in the cytosol and transported into mitochondria. Two separate ALA synthase genes encode housekeeping (tissue-nonspecific) and erythroid specific forms of the enzyme (ALAS1 and ALAS2, respectively). The gene for human ALAS1 is on 3p.21 and the locus for ALAS2 the X-chromosome, at Xp11.2.
The two forms of ALAS are differentially regulated, ALAS1 is a housekeeping gene expressed in all cells and ALAS2 is driven by erythroid specific transcription factors GATA1 and NF-E2. Additionally, ALAS2 mRNA contains an iron-responsive element (IRE) in its 5'-untranslated region, similar to mRNAs encoding ferritin and the transferrin receptor (in which the IRE is in the gene's 3' UTR). Gel retardation analysis showed that the iron-responsive element in ALAS2 mRNA is functional [as evidenced by binding to iron regulator protein 2 (IRP2)], indicating that translation of the erythroid-specific mRNA is directly linked to the availability of iron and heme in erythroid cells. In this case, when intracellular iron concentration is relatively high, it is available for binding to IRP2, a process that enhances ubiquitin-mediated degradation of IRP2. Under these conditions, IRP2 is unavailable for binding to the IRE element in ALAS2, clearing the message for efficient translation. Conversely, when intracellular iron is relatively low, IRP2 degradation is restricted, making the protein available for binding to the IRE and thereby blocking translation of ALAS2 mRNA.
Recently, a variant form of EPP, inherited in an X-linked pattern (XLEPP), was shown to be due to an ALAS2 gain-of-function mutation in exon 11. The mutation results in a truncated form of the protein that has supranormal specific activity as a result of less constrained enzyme-substrate interactions, resulting in overproduction of PPIX. This situation is in contrast to EPP with mutated FECH in which PPIX accumulates because of deficient heme formation.
ALAS1 and 2 use pyridoxal phosphate (PLP) as a cofactor. PLP is a modified form of vitamin B6. It has been shown that PLP complexes with isoniazid depleting the cofactor. This PLP depletion has been one of the causes of sideroblastic anemia.
The investigators will test the hypothesis that depletion of PLP will lead to decreased activity of ALAS.
Study Design
Arms and Interventions
| Arm | Intervention/Treatment |
|---|---|
| Experimental: Isoniazid Subjects will receive isoniazid daily for 2 months. Subjects will be seen every 2 weeks to obtain lab samples and health check. |
Drug: Isoniazid
Isoniazid 5 mg/Kg up to 300 mg per day. Oral tablets. 2 months.
|
Outcome Measures
Primary Outcome Measures
- Change in Plasma Protoporphyrin IX Level [Baseline and 3 Months]
Plasma Protoporphyrin IX will be measured at baseline and at 3 months
Secondary Outcome Measures
- Participants With Increased Sun Sensitivity [Baseline and 3 Months]
Study participants were asked to report after 3 months if they had experienced an increase in subjective measures of sun sensitivity during the trial. Reported outcome is the number of study participants who reported increased sun sensitivity
Eligibility Criteria
Criteria
Inclusion Criteria:
-
All subjects will be enrolled in the Longitudinal Study of the Porphyrias.
-
In patients with EPP the inclusion criteria are based on
-
clinical features
-
biochemical findings, as documented by laboratory reports of porphyria-specific testing performed after 1980
-
molecular findings documenting the identification of a mutation in FECH or ALAS2 genes (molecular evidence of EPP is required for inclusion in the study).
These data will be obtained from the Porphyria Rare Disease Clinical Research Consortium Longitudinal Study (RDCRN Protocol 7201). An individual must be willing to give written informed consent and be 18 years of age or greater.
Autosomal EPP (EPP) and X-linked protoporphyria (XLEPP)
Clinical features - a or b required
-
A history of non-blistering cutaneous photosensitivity, usually with early age of onset.
-
A diagnosis of EPP or XLEPP in a relative.
Biochemical findings
-
A marked increase in erythrocyte protoporphyrin [total erythrocyte protoporphyrin >200 ug/dL, or more than 1.5-fold increase relative to upper limit of normal of 80 ug/dL, with a predominance of free protoporphyrin (85-100% in EPP and 50-85% in XLEPP). Note: Methods in some laboratories for measuring free erythrocyte protoporphyrin (FEP) actually measure zinc protoporphyrin, so these results cannot be relied upon for diagnosis or characterizing the phenotype in EPP and XLEPP.
-
Increased plasma porphyrins with a fluorescence emission peak at ~634 nm.
-
Normal urinary porphyrins (except in patients with hepatobiliary impairment), and normal ALA and porphobilinogen (PBG).
Molecular findings - one of the following:
-
A disease causing FECH mutation trans to the IVS3-48C>T low expression FECH allele (aEPP)
-
Two disease-causing FECH mutations (EPP, recessive variant)
-
A gain-of-function ALAS2 C-terminal deletion/exon 11 mutation (XLEPP)
Exclusion Criteria:
-
Patients with a diagnosis of EPP that cannot be documented by DNA testing.
-
Patients with evidence of active liver injury as defined by serum transaminase concentrations greater than three times the upper limit of normal, those with a history of recent (within 3 months of enrollment) or ongoing alcohol abuse, those with diabetes mellitus requiring therapy, renal insufficiency (serum creatinine >2.0 mg/ml) or evidence of malnutrition (based on subnormal plasma concentration of transthyretin) will be ineligible for participation in the study.
-
Pregnant and/or lactating women will be excluded from the study.
Contacts and Locations
Locations
| Site | City | State | Country | Postal Code | |
|---|---|---|---|---|---|
| 1 | University of Utah School of Medicine | Salt Lake City | Utah | United States | 84132 |
Sponsors and Collaborators
- University of Utah
- National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)
- Icahn School of Medicine at Mount Sinai
- University of Alabama at Birmingham
- University of California, San Francisco
- University of Texas
Investigators
- Principal Investigator: John D Phillips, PhD, University of Utah
Study Documents (Full-Text)
None provided.More Information
Additional Information:
Publications
None provided.- UTINH
- U54DK083909
Study Results
Participant Flow
| Recruitment Details | |
|---|---|
| Pre-assignment Detail |
| Arm/Group Title | Isoniazid |
|---|---|
| Arm/Group Description | Subjects will receive isoniazid daily for 2 months. Subjects will be seen every 2 weeks to obtain lab samples and health check. Isoniazid: Isoniazid 5 mg/Kg up to 300 mg per day. Oral tablets. 2 months. |
| Period Title: Overall Study | |
| STARTED | 11 |
| COMPLETED | 10 |
| NOT COMPLETED | 1 |
Baseline Characteristics
| Arm/Group Title | Isoniazid |
|---|---|
| Arm/Group Description | Subjects will receive isoniazid daily for 2 months. Subjects will be seen every 2 weeks to obtain lab samples and health check. Isoniazid: Isoniazid 5 mg/Kg up to 300 mg per day. Oral tablets. 2 months. |
| Overall Participants | 11 |
| Age (Count of Participants) | |
| <=18 years |
0
0%
|
| Between 18 and 65 years |
11
100%
|
| >=65 years |
0
0%
|
| Gender (Count of Participants) | |
| Female |
6
54.5%
|
| Male |
5
45.5%
|
| Protoporphyria Type (Count of Participants) | |
| Erythropoietic Protoporphyria (EPP) |
9
81.8%
|
| X-linked Erythropoietic Protoporphyria (XLEPP) |
2
18.2%
|
| Baseline Protoporphyrin IX level (micrograms per deciliter (µg/dL)) [Mean (Standard Deviation) ] | |
| Mean (Standard Deviation) [micrograms per deciliter (µg/dL)] |
13.3
(14.4)
|
Outcome Measures
| Title | Change in Plasma Protoporphyrin IX Level |
|---|---|
| Description | Plasma Protoporphyrin IX will be measured at baseline and at 3 months |
| Time Frame | Baseline and 3 Months |
Outcome Measure Data
| Analysis Population Description |
|---|
| [Not Specified] |
| Arm/Group Title | Isoniazid |
|---|---|
| Arm/Group Description | Subjects will receive isoniazid daily for 2 months. Subjects will be seen every 2 weeks to obtain lab samples and health check. Isoniazid: Isoniazid 5 mg/Kg up to 300 mg per day. Oral tablets. 2 months. |
| Measure Participants | 10 |
| Mean (Standard Deviation) [µg/dL] |
0.36
(9.1)
|
| Title | Participants With Increased Sun Sensitivity |
|---|---|
| Description | Study participants were asked to report after 3 months if they had experienced an increase in subjective measures of sun sensitivity during the trial. Reported outcome is the number of study participants who reported increased sun sensitivity |
| Time Frame | Baseline and 3 Months |
Outcome Measure Data
| Analysis Population Description |
|---|
| [Not Specified] |
| Arm/Group Title | Isoniazid |
|---|---|
| Arm/Group Description | Subjects will receive isoniazid daily for 2 months. Subjects will be seen every 2 weeks to obtain lab samples and health check. Isoniazid: Isoniazid 5 mg/Kg up to 300 mg per day. Oral tablets. 2 months. |
| Measure Participants | 10 |
| Number [participants] |
0
0%
|
Adverse Events
| Time Frame | 3 Months | |
|---|---|---|
| Adverse Event Reporting Description | ||
| Arm/Group Title | Isoniazid | |
| Arm/Group Description | Subjects will receive isoniazid daily for 2 months. Subjects will be seen every 2 weeks to obtain lab samples and health check. Isoniazid: Isoniazid 5 mg/Kg up to 300 mg per day. Oral tablets. 2 months. | |
All Cause Mortality |
||
| Isoniazid | ||
| Affected / at Risk (%) | # Events | |
| Total | / (NaN) | |
Serious Adverse Events |
||
| Isoniazid | ||
| Affected / at Risk (%) | # Events | |
| Total | 1/11 (9.1%) | |
| General disorders | ||
| Flu-like Symptoms | 1/11 (9.1%) | 1 |
Other (Not Including Serious) Adverse Events |
||
| Isoniazid | ||
| Affected / at Risk (%) | # Events | |
| Total | 5/11 (45.5%) | |
| Cardiac disorders | ||
| Atrial Flutter | 1/11 (9.1%) | 1 |
| Ear and labyrinth disorders | ||
| Vertigo | 1/11 (9.1%) | 1 |
| Gastrointestinal disorders | ||
| Constipation | 1/11 (9.1%) | 1 |
| Nervous system disorders | ||
| Headache | 1/11 (9.1%) | 1 |
| Renal and urinary disorders | ||
| Urinary Tract Pain | 1/11 (9.1%) | 1 |
| Reproductive system and breast disorders | ||
| Dysmenorrhea | 1/11 (9.1%) | 1 |
| Respiratory, thoracic and mediastinal disorders | ||
| Productive Cough | 1/11 (9.1%) | 1 |
| Nasal Congestion | 1/11 (9.1%) | 2 |
Limitations/Caveats
More Information
Certain Agreements
Principal Investigators are NOT employed by the organization sponsoring the study.
There is NOT an agreement between Principal Investigators and the Sponsor (or its agents) that restricts the PI's rights to discuss or publish trial results after the trial is completed.
Results Point of Contact
| Name/Title | John D. Phillips, Ph.D. |
|---|---|
| Organization | University of Utah |
| Phone | 801-581-6650 |
| john.phillips@hsc.utah.edu |
- UTINH
- U54DK083909