Week 51 – Rifaximin Treatment in Hepatic Encephalopathy

“Rifaximin Treatment in Hepatic Encephalopathy”

N Engl J Med. 2010 Mar25;362(12):1071-81. [free full text]

As we are well aware at Georgetown, hepatic encephalopathy (HE) is highly prevalent among patients with cirrhosis, and admissions for recurrent HE place a significant burden on the medical system. The authors of this study note that HE is thought to result from “the systemic accumulation of gut-derived neurotoxins, especially ammonia, in patients with impaired liver function and portosystemic shunting.” Lactulose is considered the standard of care for the prevention of HE. It is thought to decrease the absorption of ammonia in the gut lumen through its cathartic effects and by alteration of colonic pH. The minimally absorbable oral antibiotic rifaximin is thought to further reduce ammonia production through direct antibacterial effects within the gut lumen. Thus the authors of this pivotal 2010 study sought to determine the additive effect of daily rifaximin prophylaxis in the prevention of HE.

The study enrolled adults with cirrhosis and 2+ episodes of overt HE during the past 6 months and randomized them to treatment with either rifaximin 550mg PO BID x6 months or placebo 550mg PO BID x6 months. The primary outcome was time to first breakthrough episode of HE (West Haven Score of 2+ or West Haven Score 0 –> 1 with worsening asterixis). Secondary outcomes included time to first hospitalization involving HE and adverse events, including those “possibly related to infection.”

299 patients were randomized. 140 and 159 patients were assigned to rifaximin and placebo, respectively. Baseline characteristics were similar among the two groups. Lactulose use prior to and during the study was similar in both groups at approximately 91%. Breakthrough HE occurred in 31 (22.1%) of the rifaximin patients and 73 (45.9%) of the placebo patients [HR 0.42, 95% CI 0.28-0.64, p<0.001, absolute risk reduction 23.7%, NNT = 4.2]. This result was consistent within all tested subgroups, except patients with MELD score 19-24 and patients who were not using lactulose at baseline. (See Figure 3.) Hospitalization involving HE occurred in 19 (13.6%) of the rifaximin patients and 36 (22.6%) of the placebo patients [HR 0.50, 95% CI 0.29-0.87, p = 0.01, absolute risk reduction 9.1%, NNT = 11.0]. There were no differences in adverse events among the two treatment groups.

Thus, prophylactic rifaximin reduced the incidence of recurrent HE and its resultant hospitalizations. This landmark trial showed a clear treatment benefit with implied savings in healthcare utilization costs associated with HE recurrences and hospitalizations. This marked effect was demonstrated even in the setting of relatively good (91%) lactulose adherence in both treatment arms prior to and throughout the trial.  On the day this trial was published in 2010, the FDA approved rifaximin for “reduction in risk of overt hepatic encephalopathy recurrence” in adults.

Because rifaximin is not generic and remains quite expensive, its financial utility is limited from an insurance company’s perspective. There is no other comparable nonabsorbable antibiotic for this indication. UpToDate suggests starting with lactulose therapy and then adding a nonabsorbable antibiotic, such as rifaximin, both for the treatment of overt HE and for the prevention of recurrent HE. In practice, most insurance companies will require a prior authorization for outpatient rifaximin treatment, but in my recent experience, this process has been perfunctory and easy.

Further Reading/References:
1. ClinicalTrials.gov, NCT00298038
2. FDA, NDA approval letter for Xifaxan (rifaximin)
3. UpToDate, “Hepatic encephalopathy in adults: Treatment”

Summary by Duncan F. Moore, MD

Week 50 – VERT

“Effects of Risedronate Treatment on Vertebral and Nonvertebral Fractures in Women With Postmenopausal Osteoporosis”

by the Vertebral Efficacy with Risedronate Therapy (VERT) Study Group

JAMA. 1999 Oct 13;282(14):1344-52. [free full text]

Bisphosphonates are a highly effective and relatively safe class of medications for the prevention of fractures in patients with osteoporosis. The VERT trial published in 1999 was a landmark trial that demonstrated this protective effect with the daily oral bisphosphonate risedronate.

The trial enrolled post-menopausal women with either 2 or more vertebral fractures per radiography or 1 vertebral fracture with decreased lumbar spine bone mineral density. Patients were randomized to the treatment arm (risedronate 2.5mg PO daily or risedronate 5mg PO daily) to the daily PO placebo control arm. Measured outcomes included: 1) the prevalence of new vertebral fracture at 3 years follow-up, per annual imaging, 2) the prevalence of new non-vertebral fracture at 3 years follow-up, per annual imaging, and 3) change in bone mineral density, per DEXA q6 months.

2458 patients were randomized. During the course of the study, “data from other trials indicated that the 2.5mg risedronate dose was less effective than the 5mg dose,” and thus the authors discontinued further data collection on the 2.5mg treatment arm at 1 year into the study. All treatment groups had similar baseline characteristics. 55% of the placebo group and 60% of the 5mg risedronate group completed 3 years of treatment. The prevalence of new vertebral fracture within 3 years was 11.3% in the risedronate group and 16.3% in the placebo group (RR 0.59, 95% CI 0.43-0.82, p = 0.003; NNT = 20). The prevalence of new non-vertebral fractures at 3 years was 5.2% in the treatment arm and 8.4% in the placebo arm (RR 0.6, 95% CI 0.39-0.94, p = 0.02; NNT = 31). Regarding bone mineral density (BMD), see Figure 4 for a visual depiction of the changes in BMD by treatment group at the various 6-month timepoints. Notably, change from baseline BMD of the lumbar spine and femoral neck was significantly higher (and positive) in the risedronate 5mg group at all follow-up timepoints relative to the placebo group and at all timepoints except 6 months for the femoral trochanter measurements. Regarding adverse events, there was no difference in the incidence of upper GI adverse events among the two groups. GI complaints “were the most common adverse events associated with study discontinuance,” and GI events lead to 42% of placebo withdrawals but only 36% of the 5mg risedronate withdrawals.

Oral risedronate reduces the risk of vertebral and non-vertebral fractures in patients with osteoporosis while increasing bone mineral density. Overall, this was a large, well-designed RCT that demonstrated a concrete treatment benefit. As a result, oral bisphosphonate therapy has become the standard of care both for treatment and prevention of osteoporosis. This study, as well as others, demonstrated that such therapies are well-tolerated with relatively few side effects. A notable strength of this study is that it did not exclude patients with GI comorbidities.  One weakness is the modification of the trial protocol to eliminate the risedronate 2.5mg treatment arm after 1 year of study. Although this arm demonstrated a reduction in vertebral fracture at 1 year relative to placebo (p = 0.02), its elimination raises suspicion that the pre-specified analyses were not yielding the anticipated results during the interim analysis and thus the less-impressive treatment arm was discarded.

Further Reading/References:
1. Weekly alendronate vs. weekly risedronate [https://www.ncbi.nlm.nih.gov/pubmed/15619680]
2. Comparative effectiveness of pharmacologic treatments to prevent fractures: an updated systematic review (2014) [https://www.ncbi.nlm.nih.gov/pubmed/25199883]

Summary by Duncan F. Moore, MD

Image Credit: Nick Smith, CC BY-SA 3.0, via Wikimedia Commons

Week 49 – PARADIGM-HF

“Angiotensin-Neprilysin Inhibition versus Enalapril in Heart Failure”

N Engl J Med. 2014 Sep 11;371(11):993-1004. [free full text]


Background:
Thanks to the CONSENSUS and SOLVD trials, angiotensin-converting enzyme (ACE) inhibitors have been a cornerstone of the treatment of heart failure with reduced ejection fraction (HFrEF) for years. Neprilysin is a neutral endopeptidase that degrades several peptides, including natriuretic peptides, bradykinin, and adrenomedullin. Inhibiting neprilysin increases levels of these substances and thus counteracts the neurohormonal overactivation of heart failure (which would otherwise lead to vasoconstriction, sodium retention, and maladaptive remodeling). Prior experimental data has demonstrated that, in terms of cardiovascular outcomes, neprilysin inhibition with an ARB is superior to ARB monotherapy. However, a clinical trial of concurrent neprilysin-inhibitor and ACE inhibitor therapy resulted in unacceptably high rates of serious angioedema. This study sought to show improved cardiac and mortality outcomes with neprilysin inhibition plus an ARB when compared to enalapril alone.

The study enrolled adults with NYHA class II, III, or IV heart failure, LVEF ≤ 35%, and BNP ≥ 150 or NT-proBNP ≥600. Pertinent exclusion criteria included symptomatic hypotension, SBP < 100mmHg at screening or 95mmHg at randomization, eGFR < 30 or decrease in eGFR by 25% between screening and randomization, K+ > 5.2, or history of angioedema/side effects to ACE inhibition or ARBs. Patients were randomized to treatment with either sacubitril/valsartan 200mg BID or to enalapril 10mg BID. (Screened patients were initially given sacubitril/valsartan followed by enalapril in single blinded run-in phases in order to ensure similar tolerance of the drugs prior to randomization.) The primary outcome was a composite of death from cardiovascular causes or first hospitalization for heart failure. Selected secondary outcomes included: 1) change from baseline in the clinical summary score of the Kansas City Cardiomyopathy Questionnaire (KCCQ), 2) time to new-onset atrial fibrillation, and 3) time to first occurrence of decline in renal function.

 

Results:
4187 patients were randomized to the sacubitril/valsartan group, and 4212 were randomized to the enalapril group.

The primary endpoint (composite death due to cardiovascular causes or first hospitalization for HF) occurred in 914 patients (21.8%) in the sacubitril/valsartan group and 1117 patients (26.5%) in the enalapril group (p < 0.001; NNT = 21). Death due to cardiovascular causes occurred 558 times in the sacubitril/valsartan group and 693 times in the enalapril group (13.3% vs. 16.5%, p < 0.001; NNT = 31). Hospitalization for heart failure occurred (at least once) 537 times in the sacubitril/valsartan group and 658 times in the enalapril group (12.8% vs. 15.6%, p < 0.001; NNT = 36).

Regarding secondary outcomes, the mean change in KCCQ score was a reduction of 2.99 points (i.e. a worsening of symptoms) in the sacubitril/valsartan group versus a reduction of 4.63 points in the enalapril group (p = 0.001). There was no significant group difference in time to new-onset atrial fibrillation or time to diminished renal function.

Regarding safety outcomes, patients in the sacubitril/valsartan group were more likely to have symptomatic hypotension compared to patients in the enalapril group (14.0% vs. 9.2%; p < 0.001; NNH = 21). However, patients in the enalapril group were more likely to have cough, serum creatinine ≥ 2.5, or potassium ≥6.0 compared to sacubitril/valsartan (p value varies, all significant). There was no group difference in rates of angioedema (p = 0.13).

Implication/Discussion:
In patients with HFrEF, inhibition of both angiotensin II and neprilysin with sacubitril/valsartan significantly reduced the risk of cardiovascular death or hospitalization for heart failure when compared to treatment with enalapril alone.

This study had several strengths. The treatment with sacubitril/valsartan was compared to treatment with a dose of enalapril that had previously been shown to reduce mortality when compared with placebo. Furthermore, the study used a run-in phase to ensure that patients could tolerate an enalapril dose that had previously been shown to reduce mortality. Finally, more patients in the enalapril group than in the sacubitril/valsartan group stopped the study drug due to adverse effects (12.3% vs. 10.7%, p = 0.03).

This study ushered in a new era in heart failure management and added a new medication class – Angiotensin Receptor-Neprilysin Inhibitors or ARNIs – to the arsenal of available heart failure drugs. Entresto (sacubitril/valsartan), the ARNI posterchild, has been advertised widely over the past several years. However, clinical use so far has been lower than expected (see http://www.cardiobrief.org/2017/12/05/after-slow-start-entresto-is-poised-for-takeoff/). Novartis, Entresto’s drug maker, is currently sponsoring PARAGON-HF, a trial of Entresto in patients with heart failure with preserved ejection fraction (HFpEF).

The 2017 ACC/AHA update to the guidelines for management of symptomatic HFrEF states that primary inhibition of the renin-angiotensin system with an ARNI in conjunction with evidence-based beta blockade and aldosterone antagonism is a Class I recommendation (Level B evidence). However, it does not favor this regimen over the Level-A-evidence regimens of an ARB or ACE inhibitor substituted for the ARNI. Yet the new guidelines also state that patients who have chronic symptomatic HFrEF of NYHA class II or III and tolerate an ACE inhibitor or ARB should substitute an ARNI for the ACE inhibitor or ARB in order to further reduce morbidity and mortality (Class I recommendation, level B evidence). See pages 15 and 17 here to read the details.

Bottom line:
Among patients with symptomatic HFrEF, treatment with an ARNI reduces cardiovascular mortality and HF hospitalizations when compared to treatment with enalapril. Due to this study’s impact, the use of ARNIs is now a Class I recommendation by the 2017 ACC/AHA guidelines for the treatment of HFrEF. Despite its higher cost, the use of sacubitril/valsartan appears to be cost-effective in terms of QALYs gained.

Further Reading/References:
1. PARADIGM-HF @ Wiki Journal Club
2. PARADIGM-HF @ 2 Minute Medicine
3. ACC/AHA 2017 Focused Update for Guideline Management of Heart Failure
4. CardioBrief, “After Slow Start Entresto Is Poised For Takeoff.”
5. PARAGON-HF @ ClinicalTrials.gov
6. McMurray et al., “Cost-effectiveness of sacubitril/valsartan in the treatment of heart failure with reduced ejection fraction.” Heart, 2017.

Summary by Patrick Miller, MD

Week 48 – SYMPLICITY HTN-3

“A Controlled Trial of Renal Denervation for Resistant Hypertension”

N Engl J Med. 2014 Apr 10;370(15):1393-401 [free full text]

Approximately 10% of patients with hypertension have resistant hypertension (SBP > 140 despite adherence to three maximally tolerated doses of antihypertensives, including a diuretic). Evidence suggests that the sympathetic nervous system plays a large role in such cases, so catheter-based radiofrequency ablation of the renal arteries (renal denervation therapy) was developed as a potential treatment for resistant HTN. The 2010 SYMPLICITY HTN-2 trial was a small (n=106), non-blinded, randomized trial of renal denervation vs. continued care with oral antihypertensives that demonstrated a remarkable 30-mmHg greater decrease in SBP with renal denervation. Thus the 2014 SYMPLICITY HTN-3 trial was designed to evaluate the efficacy of renal denervation in a single-blinded trial with a sham-procedure control group.

The trial enrolled adults with resistant HTN with SBP ≥ 160 despite adherence to 3+ maximized antihypertensive drug classes, including a diuretic. (Pertinent exclusion criteria included secondary hypertension, renal artery stenosis > 50%, prior renal artery intervention.) Patients were randomized to either renal denervation with the Symplicity (Medtronic) radioablation catheter or to renal angiography only (sham procedure). The primary outcome was the mean change in office systolic BP from baseline at 6 months. (The examiner was blinded to intervention.) The secondary outcome was the change in mean 24-hour ambulatory SBP at 6 months. The primary safety endpoint was a composite of death, ESRD, embolic event with end-organ damage, renal artery or other vascular complication, hypertensive crisis within 30 days, or new renal artery stenosis of > 70%.

535 patients were randomized. On average, patients were receiving five antihypertensive medications. There was no significant difference in reduction of SBP between the two groups at 6 months. ∆SBP was -14.13 ± 23.93 mmHg in the denervation group vs. -11.74 ± 25.94 mmHg in the sham-procedure group for a between-group difference of -2.39 mmHg (95% CI -6.89 to 2.12, p = 0.26 with a superiority margin of 5 mmHg). The change in 24-hour ambulatory SBP at 6 months was -6.75 ± 15.11 mmHg in the denervation group vs. -4.79 ± 17.25 mmHg in the sham-procedure group for a between-group difference of -1.96 mmHg (95% CI -4.97 to 1.06, p = 0.98 with a superiority margin of 2 mmHg). There was no significant difference in the prevalence of the composite safety endpoint at 6 months with 4.0% of the denervation group and 5.8% of the sham-procedure group reaching the endpoint (percentage-point difference of -1.9, 95% CI -6.0 to 2.2).

In patients with resistant hypertension, renal denervation therapy provided no reduction in SBP at 6-month follow-up relative to a sham procedure.

This trial was an astounding failure for Medtronic and its Symplicity renal denervation radioablation catheter. The magnitude of the difference in results between the non-blinded, no-sham-procedure SYMPLICITY HTN-2 trial and this patient-blinded, sham-procedure-controlled trial is likely a product of 1) a marked placebo effect of procedural intervention, 2) Hawthorne effect in the non-blinded trial, and 3) regression toward the mean (patients were enrolled based on unusually high BP readings that over the course of the trial declined to reflect a lower true baseline).

Currently, there is no role for renal denervation therapy in the treatment of HTN (resistant or otherwise). However, despite the results of SYMPLICITY HTN-3, other companies and research groups are assessing the role of different radioablation catheters in patients with low-risk essential HTN and with resistant HTN. (For example, see https://www.ncbi.nlm.nih.gov/pubmed/29224639.)

Further Reading/References:
1. NephJC, SYMPLICITY HTN-3
2. UpToDate, “Treatment of resistant hypertension,” heading “Renal nerve denervation”

Summary by Duncan F. Moore, MD