Why Some Genetic Mutations May Be Helpful: HFE

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When one looks at diseases, it is important to consider that the mutations that cause the disease may confer other selective advantages.

A classic example has been sickle-cell disease.  The heterozygous state is usually asymptomatic and makes an individual less prone to malaria.  “In the USA, where there is no endemic malaria, the prevalence of sickle-cell anaemia among blacks is lower (about 0.25%) than in West Africa (about 4.0%) and is falling. Without endemic malaria, the sickle cell mutation is purely disadvantageous and will tend to be selected out of the affected population via natural selection.” —Sickle–cell disease – Wikipedia, the free encyclopedia

Another common disorder is hemochromatosis.  A recent letter in the New England Journal of Medicine (NEJM 2013; 369: 785-6) explains why having the HFE gene could be advantageous.  According to the authors the genetic mutation arose in Celtic populations who were notably taller than other populations.  As such, the authors hypothesized that the patients with HFE hemochromatosis would have better growth by having an abundant supply of iron during periods of rapid development.

They assessed a cohort of 176 Swiss patients with HFE hemochromatosis.  93% were homozygous for the C282Y mutation, 7% had a compound H63D-C282Y mutation.  All of the patients had verified iron overload determined as a ferritin > 300 mcg/L or a transferrin saturation >45%.

Compared with an age-matched, sex-matched Swiss reference population, men with hemochromatosis (n=120) were 4.3 cm taller on average. In women (n=56), the difference was 3.3 cm.  To avoid bias due to population origin, the cohort was also compared with data from Ireland where the data remained validated.

Take-home message: Extra iron in the first two decades of life promote better growth (and probably other advantages).  However, iron overload later in life can lead to cirrhosis, diabetes, heart disease, and reproductive problems.

Related blog post:

AASLD Hemochromatosis Guidelines:

Anti-TNF therapy for IBD

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In the same issue as the vedolizumab phase 3 studies, there is a succinct review of tumor necrosis antagonist therapy (anti-TNF) therapy for IBD (NEJM 2103; 369: 754-62).

Useful points about IBD:

  • Prevalence of ulcerative colitis (UC) and Crohn’s disease (CD) in North America: 780,000 and 630,00 respectively
  • In first 10 years of CD, cumulative rate of surgery is 40-55%.
  • In first 20 years of UC, rate of colectomy is ~15%.
  • “Recent meta-analysis do not indicate that this drug (mesalamine) has any clinically relevant efficacy in patients with” Crohn’s disease.

Anti-TNF agents:

  • Agents for IBD include infliximab, adalimumab, certolizumab pegol, and golimumab.
  • No head-to-head comparisons have been studied, though the “clinical trials suggest similar efficacy among the available drugs.”
  • Newest approved anti-TNF is golimumab which is administered subcutaneously at a dose of 200 mg at week 0, followed by 100 mg at week 2 and then 100 mg every 4 weeks.
  • A “considerable number of patients with Crohn’s disease (10-40%, depending on selection criteria) do not have a clinically relevant response to currently available TNF inhibitors (primary treatment failure) and among patients with ulcerative colitis, this proportion may be as high as 50%.”
  • “In addition, only about one third to one half of patients with Crohn’s disease have a complete remission, and about two thirds of patients do not have a response that is sustained during 12 months of continuous treatment (secondary treatment failure).”  Many of these patients will respond to dose escalation.
  • The “annual projected cost of each biologic agent for a 70-kg patient with inflammatory bowel disease is approximately $19,000 in the first year and $15,000 in subsequent years.”  These figures exclude the costs associated with administration and dose escalation.

Areas of uncertainty according to the authors:

  • “The value of concomitant treatment with immunosuppressive agents and TNF inhibitors has been debated intensely.”  Combination therapy results in superior efficacy and lower rates of antibodies to anti-TNF agents.  However, “the benefit of combined treatment for more than 12 months is uncertain.”
  • “There are no data to confirm that it (top-down treatment) is actually superior to conventional step-up therapy in terms of disease progression”

Related blog links:

Coming Soon to a Pharmacy Near You (part 2)…

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While yesterday’s post reviewed the data that indicate that vedolizumab is likely to be helpful for ulcerative colitis, only small improvements were noted for patients with Crohn’s disease (NEJM 2013; 369: 711-21, GEMINI 2 studies).

Vedolizumab, “a humanized immunoglobulin G1 monoclonal antibody to α4β7 integrin, modulates gut, but not brain, lymphocyte trafficking.”  The GEMINI 2 studies for Crohn’s disease were similar to the GEMINI 1 studies for UC.  However, even more medical centers (n=285) in more countries (n=39) and more patients (n=1115 with 967 receiving study drug) participated.

Baseline characteristics:

  • Median age: 36.1 years
  • Current Smokers: 26.7%
  • Disease location: 16.2% ileum only, 28.3% colon only, 55.4% ileum/colon
  • Median fecal calprotectin: 686 mcg/gram
  • Concomitant medications: 34.2% steroids only, 16.2% immunosuppressives only, 17% both steroids and immunosuppressives, 32.6% neither steroids or immunosuppressives
  • Median steroid dosage: 20 mg
  • Prior TNF antagonist ≥1:  61.8%
  • Prior surgery for Crohn’s disease: 41.8%
  • Prior fistulizing disease: 36.8%

Results:

  • At week 6, 14.5% of vedolizumab-treated patients and 6.8% of placebo-treated patients were in clinical remission (CDAI ≤150).
  • At week 6, 31.4% of study drug group and 25.7% of placebo group had a CDAI-100 response (≥ 100 point decrease in CDAI score).
  • Among patients with an induction response, 39% and 36.4% of vedolizumab every 8 weeks and every 4 weeks, respectively were in clinical remission at week 52, compared with 21.6% of patients assigned to placebo.
  • Vedolizumab-treated patients had increased serious adverse effects including serious infections.  Nasopharyngitis occurred more frequently.
  • Five deaths were noted during the study, four among the treatment group (Crohn’s/sepsis, intentional overdose, myocarditis, and septic shock).
  • No PML cases have been reported among the 3000 patients exposed to vedolizumab

While the response rate to vedolizumab was modest in Crohn’s disease patients, there are some factors that need to be considered in interpreting this data. Unlike in many trials (According to the study which you would never … – gutsandgrowth), this trial included patients with more disease severity.  The authors note that the effects of anti-integrin therapy could be relatively slower acting in Crohn’s disease due to the transmural nature of the disease.  An alternative explanation would be that the gut-selective targeting by vedolizumab is ineffective in most patients with Crohn’s disease due to the need for a more systemic inhibition with transmural disease.

Bottom-line: Among the small percentage of patients who have a response to vedolizumab at week 6, the rates of clinical remission at week 52 were significantly higher than those who received placebo.

Coming Soon to a Pharmacy Near You (part 1)…

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Vedolizumab!

Two articles indicate that Vedolizumab will be an important agent for treating Ulcerative Colitis (UC).  The first article, NEJM 2013; 369: 699-710, describes two integrated studies (GEMINI 1 studies) in the use of this agent for induction and then for maintenance therapy of UC.

Background: Vedolizumab is a gut-selective blocker of lymphocyte trafficking (see previous post: Vedolizumab -another new IBD treatment | gutsandgrowth).  It is similar to natalizumab which was approved in 2008 for Crohn’s disease.  In phase 3 trials, natalizumab was demonstrated a response in 48% of patients with moderate-to-severe disease, but its large-scale use has been precluded by the potential for reactivation of the John Cunningham (JC) virus and progressive multifocal leukoencephalopathy (PML).

Study design: this study was a phase 3, randomized, double-blind, placebo-controlled study conducted at 211 medical centers in 34 countries from 2008-2012.  At baseline some of the assessments included blood tests, stool for enteric pathogens, chest radiography, stool calprotectin, QuantiFERON-TB Gold assay and sigmoidoscopy.  Intravenous vedolizumab was administered at a dose of 300 mg or placebo at days 1 and 15 during induction; also patients were stratified for glucocorticosteroids, use of immunosuppressives and prior use of TNF antagonists.  In total, 746 patients received vedolizumab and 149 received placebo.

Some of the baseline patient characteristics:

  • Mean age: 40.3 yrs
  • Median prednisone dose: 20 mg
  • Average fecal calprotectin: 899 mcg/gr.
  • Site of disease: 37% pancolitis, 13% rectum/sigmoid only, 37.9% left-sided disease, 12.2% disease proximal to splenic flexure.
  • Prior anti-TNF therapy: 48.2%

Results:

  • Induction: at week 6, 47.1% of vedolizumab and 25.5% of placebo-treated patients had a clinical response
  • Maintenance: at week 52, of patients randomly assigned to continue receiving vedolizumab, 44.8% every 4 weeks, 41.8% every 8 weeks were in clinical remission compared with 15.9% receiving placebo
  • Glucocorticoid-free remission at 52 weeks in 45.2% of patients receiving vedolizumab every 4 weeks, 31.4% receiving every 8 week treatment, and 13.9% of placebo-treated patients.
  • Figure 1 details important changes in Partial Mayo score, IBDQ score, Fecal calprotectin, and prednisone dose changes.  With regard to fecal calprotectin, at week 6 the median calprotectin level had dropped approximately 70%.  Smaller decreases were noted in patients continuing vedolizumab at week 52.
  • Safety: “no important differences” according to the authors between vedolizumab and placebo.  Specifically, there were no cases of PML; however, routine JC virus testing was not performed in this study.  Infusion reactions were seen in three cases (two with detectable antibody). a mild increase in nasopharyngitis was noted.
  • Cancer: 1.1% of placebo-treated patients developed a malignancy (1 colon cancer, 1 transitional-cell carcinoma, 1 squamous-cell carcinomas of skin) and 0.2% of vedolizumab (1 colon cancer)
  • Drug levels: mean vedolizumab concentrations at every 4 week dosing: 38.3 mcg/mL and at every 8 week dosing: 11.2 mcg/mL
  • Antibodies: 3.7% had samples that were positive for anti-vedolizumab antibodies at any time.  1% developed persistent antibody positivity.

Bottom-line: This large study shows that vedolizumab is effective in a large number of patients with UC, many who were refractory to other treatments, including anti-TNF agents.

Related blog posts:

Looking at the Tenofovir Data Another Way

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In last Friday’s post, this blog reviewed 5-year data on tenofovir usage which showed that tenofovir could reverse fibrosis/cirrhosis.  Another study using the same cohort examined the efficacy of tenofovir in patients with high viral load (HVL) at baseline (Hepatology 2013; 58: 505-13).

From an initial total of 641 patients enrolled in GS-US-174-0102 (n=375) and GS-US-174-0103 (n=266), the authors identified 129 (20%) with HVL.  HVL was defined as having ≥9 log10 copies/mL.  After an initial 48 weeks of randomization between tenofovir (HVL n=82) or adefovir (HVL n=47), patients received an additional 192 weeks of therapy with tenofovir in an open label extension.

Results:

  • By week 240, 98.3% of HVL and 99.2% of non-HVL patients on treatment achieved HBV DNA <400 copies/mL
  • High HVL patients took longer to achieve undetectable HBV DNA, but by week 96 the results were similar in both groups
  • Patients who received tenofovir during the initial 48 weeks achieved undetectable HBV DNA quicker than those who had received adefovir initially
  • There were similar rates of histologic regression in both HVL and non-HVL patients

This study evaluated only patients in the ‘immune clearance’ phase of HBV and therefore cannot be extrapolated to those in the immune tolerant phase.

Injection Flu Vaccine Safe for Patients with IBD

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A recent article from Pediatrics, published online May 6, 2013
(doi: 10.1542/peds.2012-3567), confirms that influenza vaccination (injection/inactivated vaccine) is safe in patients with inflammatory bowel disease:

“Safety and Utilization of Influenza Immunization in Children With Inflammatory Bowel Disease”  Eric I. Benchimol, Steven Hawken, Jeffrey C. Kwong, and Kumanan Wilson

Abstract:

OBJECTIVE: Influenza immunization is recommended for children with IBD, however safety concerns may limit uptake. This study assessed whether immunization was associated with adverse events in IBD patients using a population-based database of children with IBD.

METHODS: All children <19 years diagnosed with IBD in Ontario, Canada between 1999–2009 were identified using health administrative data, and matched to non-IBD controls. Self-controlled case series (SCCS) analyses determined health services event rates (outpatient visits, hospitalizations and emergency visits) in any 2-week risk period to 180 days post-immunization compared to a no-risk control period. Relative incidence (RI) was calculated for overall and IBD-related events and rates were compared between IBD cases and controls using relative incidence ratios (RIR).

RESULTS: 4916 IBD patients were matched to 21,686 controls. IBD patients were more likely to have received immunization than controls (25.3% vs. 13.2%, P < .001). No increased event rates existed in IBD cases during risk periods (pooled RI 0.95, 95% CI 0.84–1.07), including hospitalizations and emergency visits. There was a slightly higher event rate in IBD cases versus controls for days 3–14 (RIR 1.60, 95% CI 1.05–2.44, P = .03). IBD-related visit rates were lower in risk periods compared to control period (pooled RI 0.81, 95% CI 0.68–0.96).

CONCLUSIONS: There was no increase in health services use in the post-vaccine risk period in IBD patients, and there was evidence for a protective effect of influenza immunization against IBD-related health services use. Influenza immunization is safe in children with IBD and should be encouraged to improve poor coverage rates.

Gluten-free, Casein-free -No Improvement in Autism

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From Kipp Ellsworth’s twitter feed:

The gluten-free, casein-free diet and autism: limited return on family investment

From Journal of Early Intervention

goo.gl/uulzis  (link to entire article)

Excerpt:

Abstract

The gluten-free, casein-free (GFCF) diet is widely used by families of children with autism spectrum disorders (ASD). Despite its popularity, there is limited evidence in support of the diet. The purpose of this article was to identify and evaluate well-controlled studies of the GFCF diet that have been implemented with children with ASD. A review of the literature from 1999 to 2012 identified five studies meeting inclusion criteria. Research rigor was examined using an evaluative rubric and ranged fromAdequate to Strong. In three of the studies, no positive effects of the diet were reported on behavior or development, even after double-blind gluten and casein trials. Two studies found positive effects after 1 year but had research quality concerns. Reasons why families continue to expend effort on GFCF diets despite limited empirical evidence are discussed. Recommendations are that families should invest time and resources in more robustly supported interventions and limit GFCF diets to children diagnosed with celiac disease or food allergies.

Changing the Outcome for Hepatitis B

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Much of hepatology relies on surrogate markers to convey whether treatments are effective.  For hepatitis B virus (HBV), some of these markers include serology (eg. development of HBV e antibody), improvements in biochemistry (eg. transaminases) as well as histology.  Of these, improved histology is likely to have the most bearing on clinical outcomes like progression to end-stage liver disease and hepatocellular carcinoma.  A previous study of lamivudine has indicated that regression of fibrosis can reduce the rate of hepatocellular carcinoma (NEJM 2004; 351: 1521-31).

As such, the results of long-term use of agents like tenofovir have been awaited.  Since tenofovir along with entecavir are considered 1st line agents, their use has become commonplace for the treatment of HBV.  Now 5-year data are available in a large cohort (Lancet 2013; 381: 468-75).

The data from this study was derived from an open-label cohort that followed 48-week double-blind comparison trials. 489 patients completed 240 weeks of treatment.  348 patients had biopsy results available at baseline and at week 240.

Key findings:

  • 304 (87%) of those with biopsies at study completion had histologic improvement.
  • 176 (51%) had regression of fibrosis
  • 71 of 96 (74%) who had cirrhosis at baseline no longer had cirrhosis (≥1 unit decrease in Ishak fibrosis score)
  • 3 of 252 without cirrhosis at baseline progressed to cirrhosis at week 240
  • No evidence of resistance to tenofovir was evident.  Nearly all patients on tenofovir had undetectable HBV DNA
  • Adverse safery events were rare

As with all studies looking at liver histology, there were limiting factors including potential sampling errors and variable interpretation.  The authors sought to minimize this by using an independent pathologist.   Another strength of the study was the broad range of patients to make these findings broadly applicable.

Take-home message: Tenofovir treatment for 5 years is safe and effective.  Long-term suppression of HBV can lead to regression of fibrosis and reversal of cirrhosis.

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Fundoplication in children with neurologic impairment

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A recent study questions the value of fundoplication in children with neurologic impairment who undergo gastrostomy tube placement (JAMA Pediatr doi:10.1001/jamapediatrics.2013.334).

This paper’s findings are limited by the study’s design as a retrospective, observational cohort study.  However, the study has several strengths as well.  First of all, this was a large study which identified 4163 neurologically-impaired infants who underwent either tube placement with (n=1404) or without fundoplication (n=2759).  This population was drawn from 42,796 infants admitted to neonatal intensive care units from 42 children’s hospitals.  Thus, a second advantage of this study was looking at a broad range of children from the same NICU population.

Findings:

  • Infants who underwent fundoplication did not have a reduced rate of reflux-related hospitalizations.  The authors tried to control for differences in the population with propensity score-matched analysis.
  • Only a small number had a significant preoperative GERD workup.  In total, 9.4% of infants had pH probes and 4.3% had endoscopies preoperatively.
  • Mean number of reflux-related admissions (Table 3 in study) within 1 year after discharge from NICU: overall: for gtube 0.92 compared with 1.02 for gtube/fundo, for pneumonia 0.18 (Gtube) compared with 0.23 (Gtube/fundo), aspiration pneumonia was 0.08 for both groups.

The authors note that two previous studies had shown a reduction in reflux-related hospitalizations for children who had admissions due to reflux-related conditions.  However, they note that in their study, these patients had fundoplication performed prophylactically based on clinical judgement.

But, “clinical symptoms, including dysfunctional swallowing and intolerance of gastric feedings, likely influence the decision to perform a concomitant fundoplication; however, these were unavailable in the database.”  As such, the authors propensity score model could have failed to account for factors that are essential in deciding whether a concomitant fundoplication is worthwhile.

Bottom-line: A fundoplication may not effectively prevent reflux-related hospitalizations in neurologically-impaired infants; its expected benefits may be overstated.  The only way to definitively determine how useful (or how ineffective) a fundoplication is would be a prospective study.

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