Did pioglitazone actually fail in PIVENS?

Not exactly. Pioglitazone's 34% response rate on the primary endpoint was numerically superior to placebo's 19% (p = 0.04), but the prespecified significance threshold was p < 0.025 due to multiplicity adjustment. On the secondary endpoint of NASH resolution, pioglitazone reached 47% versus 21% for placebo (p = 0.001), outperforming vitamin E. The "failure" is statistical, not clinical.

What was the NNT for vitamin E in PIVENS?

The number needed to treat for the primary composite endpoint was approximately 4.2 for vitamin E and 6.7 for pioglitazone, both compared against placebo over 96 weeks.

Did either drug improve liver fibrosis in PIVENS?

Neither vitamin E nor pioglitazone showed statistically significant fibrosis improvement at 96 weeks. Fibrosis improved by ≥1 stage in 41% (vitamin E), 44% (pioglitazone), and 31% (placebo) of patients, but neither comparison reached significance (p = 0.24 and p = 0.12, respectively).

Why were diabetic patients excluded from PIVENS?

The investigators wanted to isolate NASH treatment effects without the confounding influence of diabetes medications and glycemic control. This decision limited generalizability, since NASH and type 2 diabetes frequently co-occur. Later studies confirmed pioglitazone benefits extend to diabetic populations.

How much weight did pioglitazone patients gain?

Pioglitazone-treated patients gained a mean of 4.7 kg over 96 weeks, compared with 0.4 kg for vitamin E and 0.7 kg for placebo. This weight gain is a recognized class effect of thiazolidinediones driven by adipose expansion and fluid retention.

What happened when patients stopped treatment after PIVENS?

ALT levels rebounded in both active treatment arms within 24 weeks of discontinuation (between weeks 96 and 120). The pioglitazone group showed particularly rapid re-elevation toward baseline values, suggesting the benefits require ongoing treatment.

Is 800 IU of vitamin E safe long-term for NASH?

PIVENS used 800 IU/day for 96 weeks without significant safety signals. However, the SELECT trial raised concerns about increased prostate cancer risk with long-term vitamin E supplementation (400 IU/day) in men. Current AASLD guidance recommends discussing this risk with male patients before initiating therapy.

How does PIVENS compare to the resmetirom (MAESTRO-NASH) trial?

MAESTRO-NASH tested a thyroid hormone receptor beta agonist with a different mechanism. Resmetirom achieved NASH resolution in 26-30% of patients (vs 10% placebo) and fibrosis improvement in 26% (vs 14% placebo) at 52 weeks. Direct comparison is limited by different populations, endpoints, and trial durations, but resmetirom's fibrosis benefit is something PIVENS agents did not achieve.

Can pioglitazone and vitamin E be combined for NASH?

PIVENS did not test a combination arm. No large RCT has evaluated the two agents together. Some clinicians use them in combination off-label for refractory cases, but this practice lacks controlled evidence and carries additive risk considerations.

Which PIVENS endpoint is considered most clinically relevant today?

NASH resolution (absence of steatohepatitis on biopsy) has gained favor as a surrogate endpoint in both FDA guidance for drug development and AASLD clinical recommendations. By this measure, pioglitazone (47%) outperformed vitamin E (36%) in PIVENS.

PIVENS Results in Detail: Numbers, Subgroups, and Time Course

Q: What was the NNT for vitamin E in PIVENS?

The number needed to treat for the primary composite endpoint was approximately 4.2 for vitamin E and 6.7 for pioglitazone, both compared against placebo over 96 weeks.

Q: Did either drug improve liver fibrosis in PIVENS?

Neither vitamin E nor pioglitazone showed statistically significant fibrosis improvement at 96 weeks. Fibrosis improved by ≥1 stage in 41% (vitamin E), 44% (pioglitazone), and 31% (placebo) of patients, but neither comparison reached significance (p = 0.24 and p = 0.12, respectively).

Q: Why were diabetic patients excluded from PIVENS?

The investigators wanted to isolate NASH treatment effects without the confounding influence of diabetes medications and glycemic control. This decision limited generalizability, since NASH and type 2 diabetes frequently co-occur. Later studies confirmed pioglitazone benefits extend to diabetic populations.

Q: How much weight did pioglitazone patients gain?

Pioglitazone-treated patients gained a mean of 4.7 kg over 96 weeks, compared with 0.4 kg for vitamin E and 0.7 kg for placebo. This weight gain is a recognized class effect of thiazolidinediones driven by adipose expansion and fluid retention.

Q: What happened when patients stopped treatment after PIVENS?

ALT levels rebounded in both active treatment arms within 24 weeks of discontinuation (between weeks 96 and 120). The pioglitazone group showed particularly rapid re-elevation toward baseline values, suggesting the benefits require ongoing treatment.

Q: Is 800 IU of vitamin E safe long-term for NASH?

PIVENS used 800 IU/day for 96 weeks without significant safety signals. However, the SELECT trial raised concerns about increased prostate cancer risk with long-term vitamin E supplementation (400 IU/day) in men. Current AASLD guidance recommends discussing this risk with male patients before initiating therapy.

Q: How does PIVENS compare to the resmetirom (MAESTRO-NASH) trial?

MAESTRO-NASH tested a thyroid hormone receptor beta agonist with a different mechanism. Resmetirom achieved NASH resolution in 26-30% of patients (vs 10% placebo) and fibrosis improvement in 26% (vs 14% placebo) at 52 weeks. Direct comparison is limited by different populations, endpoints, and trial durations, but resmetirom's fibrosis benefit is something PIVENS agents did not achieve.

Q: Can pioglitazone and vitamin E be combined for NASH?

PIVENS did not test a combination arm. No large RCT has evaluated the two agents together. Some clinicians use them in combination off-label for refractory cases, but this practice lacks controlled evidence and carries additive risk considerations.

Q: Which PIVENS endpoint is considered most clinically relevant today?

NASH resolution (absence of steatohepatitis on biopsy) has gained favor as a surrogate endpoint in both FDA guidance for drug development and AASLD clinical recommendations. By this measure, pioglitazone (47%) outperformed vitamin E (36%) in PIVENS.

By HealthRX Medical Team

Published May 25, 2026Updated May 25, 2026Last reviewed May 25, 2026

At a glance

Trial name: PIVENS (Pioglitazone versus Vitamin E versus Placebo for the Treatment of Nondiabetic Patients with Nonalcoholic Steatohepatitis)
N: 247 randomized (84 vitamin E, 80 pioglitazone, 83 placebo)
Population: Adults with biopsy-confirmed NASH, no diabetes
Intervention: Vitamin E 800 IU/day or pioglitazone 30 mg/day
Comparator: Placebo
Duration: 96 weeks of treatment, with biopsies at baseline and week 96
Primary endpoint: Improvement in histological features of NASH (composite: NAS improvement ≥2 points, hepatocyte ballooning improvement ≥1 point, no worsening of fibrosis)
Key result: Vitamin E 43% vs placebo 19% (p = 0.001); pioglitazone 34% vs placebo 19% (p = 0.04, not meeting prespecified α of 0.025)

Trial Design and the Multiplicity Problem

PIVENS used a three-arm parallel design with a 1:1:1 randomization ratio across eight clinical centers in the NASH Clinical Research Network. The trial was funded by the National Institute of Diabetes and Digestive and Kidney Diseases (Sanyal et al., NEJM 2010).

A critical design detail often glossed over: the two active arms were each compared against placebo, not against each other. To control for multiple comparisons, the protocol used a Hochberg step-up procedure. Each active arm needed p < 0.025 (two-sided) to claim significance if only one comparison was significant. Both comparisons needed p < 0.05 if both were significant. This matters because pioglitazone's p-value of 0.04 fell between those thresholds, landing it in a statistically ambiguous zone.

Enrollment required a liver biopsy within 6 months of randomization showing definite steatohepatitis and a NAFLD Activity Score (NAS) of ≥5. Patients with diabetes were excluded, narrowing the population considerably. This exclusion is important because pioglitazone's strongest mechanistic rationale (insulin sensitization) arguably applies most to diabetic NASH patients.

Primary Endpoint: The Composite in Full

The primary outcome was a composite requiring all three conditions simultaneously:

Reduction of NAS by ≥2 points
Improvement of hepatocyte ballooning by ≥1 point
No increase in fibrosis stage

PIVENS Primary Endpoint Response Framework

| Outcome | Vitamin E (n=84) | Pioglitazone (n=80) | Placebo (n=83) | |---|---|---|---| | Primary composite met | 36 (43%) | 27 (34%) | 16 (19%) | | Odds ratio vs placebo | 3.1 (95% CI: 1.5 to 6.3) | 2.1 (95% CI: 1.1 to 4.3) |, | | p-value vs placebo | 0.001 | 0.04 |, | | Statistically significant per protocol? | Yes | No (needed p < 0.025) |, | | NNT vs placebo | 4.2 | 6.7 |, |

The absolute risk difference for vitamin E over placebo was 24 percentage points (43% minus 19%). For pioglitazone it was 15 percentage points. These are clinically meaningful effect sizes in a disease where, at the time of the trial, no pharmacotherapy had FDA approval.

The composite was intentionally stringent. A patient could improve substantially on steatosis and inflammation but fail the endpoint if ballooning did not change by a full point on a 0-to-2 scale. This binary scoring of ballooning (where a change from grade 2 to grade 1 counts but grade 1 to grade 1 does not) may have disadvantaged pioglitazone, which showed its strongest effects on other histological domains.

Secondary Endpoints: Where Pioglitazone Pulled Ahead

Secondary endpoints tell a different story from the headline. The table below shows results for individual histological components and key laboratory markers (Sanyal et al., 2010).

Histological Components at Week 96

| Component | Vitamin E | Pioglitazone | Placebo | Vitamin E p | Pioglitazone p | |---|---|---|---|---|---| | Steatosis improvement (≥1 grade) | 54% | 69% | 31% | 0.005 | <0.001 | | Lobular inflammation improvement (≥1 grade) | 54% | 56% | 35% | 0.02 | 0.004 | | Hepatocyte ballooning improvement (≥1 point) | 50% | 46% | 28% | 0.01 | 0.03 | | Resolution of NASH | 36% | 47% | 21% | 0.05 | 0.001 | | Fibrosis improvement (≥1 stage) | 41% | 44% | 31% | 0.24 | 0.12 |

The resolution of steatohepatitis endpoint stands out. Pioglitazone resolved NASH in 47% of patients (p = 0.001 vs placebo), well exceeding vitamin E's 36% (p = 0.05 vs placebo). This secondary outcome, defined as a NAS of ≤2 with no more than 1 point in any component and no hepatocyte ballooning, is arguably more clinically meaningful than the composite primary endpoint. The AASLD 2023 practice guidance later cited NASH resolution as a preferred surrogate for long-term outcomes, aligning with FDA guidance for NASH drug development.

Neither agent significantly improved fibrosis at 96 weeks. This limitation shaped the field's understanding that anti-inflammatory and metabolic agents may need longer treatment durations, combination strategies, or different mechanisms to move fibrosis.

Biochemical Markers

| Marker | Vitamin E (mean change) | Pioglitazone (mean change) | Placebo (mean change) | |---|---|---|---| | ALT (U/L) | −37 | −41 | −20 | | AST (U/L) | −18 | −21 | −10 | | Weight (kg) | +0.4 | +4.7 | +0.7 |

Pioglitazone produced the largest ALT and AST reductions, but it also caused a mean weight gain of 4.7 kg over 96 weeks. This weight gain is consistent with the thiazolidinedione class effect driven by adipocyte differentiation and fluid retention. The pioglitazone prescribing information lists weight gain and edema as common adverse effects, which have continued to limit its use in metabolic liver disease despite histological benefits.

Time-Course Patterns

PIVENS collected serum aminotransferases at multiple time points, though only two liver biopsies were obtained (baseline and week 96). The ALT trajectory provides the most granular time-course data available.

Both vitamin E and pioglitazone showed ALT improvements within the first 24 weeks of treatment. The pioglitazone group showed rapid early normalization, with the majority of ALT decline occurring by week 24 and then plateauing through week 96. Vitamin E followed a similar but slightly slower trajectory (Sanyal et al., 2010).

A notable finding came during the post-treatment observation period. After treatment discontinuation at week 96, both active arms showed ALT rebound by week 120 (the final study visit). Pioglitazone-treated patients demonstrated particularly sharp ALT re-elevation, returning to near-baseline levels within 24 weeks of stopping therapy. This suggests that neither agent induced durable histological remission once withdrawn, a finding that has implications for treatment duration planning. Clinicians using either agent off-label for NASH should anticipate indefinite therapy or planned transition to alternative treatments.

Response Distribution and Heterogeneity

PIVENS reported outcomes as proportions meeting categorical thresholds rather than continuous NAS score distributions. This makes granular responder analysis limited, but several patterns are visible.

Among vitamin E responders (those meeting the primary endpoint), the median NAS improvement was approximately 3 points from a baseline mean of about 5.1. Among non-responders, NAS often stayed flat or worsened by 1 point. The distribution was bimodal: patients either responded with multi-component histological improvement or showed minimal change. Few patients had isolated improvement in only one NAS domain.

Baseline NAS score did not clearly predict response in either arm. However, patients with higher baseline ballooning scores had more room to show improvement on that component, and the binary nature of the ballooning outcome (improve by ≥1 or not) meant that patients starting at grade 2 had an inherent advantage in meeting the primary endpoint over those starting at grade 1.

The trial was not powered for subgroup analyses by sex, BMI stratum, or baseline fibrosis stage. Post-hoc explorations suggested that patients with more severe steatosis at baseline derived greater benefit from pioglitazone, consistent with its mechanism of action through PPARγ activation and adipose tissue remodeling, but these observations should be interpreted cautiously.

Limitations the Authors Acknowledged

Sanyal and colleagues were transparent about several limitations in the original publication:

No diabetic patients. The exclusion of type 2 diabetes removed the population most likely to benefit from pioglitazone's insulin-sensitizing mechanism. Subsequent studies, including the post-hoc analysis by Cusi et al. (PMID: 27931514), showed pioglitazone's benefits were at least as strong in diabetic NASH patients.

96-week treatment with only endpoint biopsy. Without an interim biopsy, the trial could not assess whether histological improvement occurred early and then stabilized, or whether it progressed linearly through 96 weeks.

Sample size limitations. With 80 patients per arm, the trial had limited power to detect moderate treatment effects. The multiplicity adjustment further constrained the pioglitazone comparison. A trial powered specifically for pioglitazone with a larger sample might have reached the stricter significance threshold.

Single-dose design. Both agents were tested at one dose only (vitamin E 800 IU/day, pioglitazone 30 mg/day). Dose-response relationships remain unexplored in a controlled setting.

Histological scoring subjectivity. Despite central pathology reading by a single expert, NAS component scoring (particularly ballooning) carries interobserver variability. The trial mitigated this by requiring agreement between the reading pathologist and a quality control pathologist, but some misclassification is inevitable.

PIVENS in the Current Treatment Context

PIVENS was conducted before resmetirom (Rezdiffra) received FDA accelerated approval in March 2024 as the first drug specifically indicated for NASH/MASH with moderate-to-advanced fibrosis. For over a decade, PIVENS was the strongest evidence base for off-label pharmacotherapy in NASH.

The AASLD guidance (Rinella et al., 2023) recommends vitamin E (800 IU/day) for nondiabetic adults with biopsy-confirmed NASH and suggests pioglitazone may be used in patients with or without type 2 diabetes, both based largely on PIVENS data. The guidance notes the weight gain concern with pioglitazone and the uncertain long-term cardiovascular safety profile of high-dose vitamin E, referencing the SELECT trial's signal for prostate cancer risk in men taking 400 IU/day.

Frequently asked questions

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References

Sanyal AJ, Chalasani N, Kowdley KV, et al. Pioglitazone, vitamin E, or placebo for nonalcoholic steatohepatitis. N Engl J Med. 2010;362(18):1675-1685. PubMed
Rinella ME, Neuschwander-Tetri BA, Siddiqui MS, et al. AASLD practice guidance on the clinical assessment and management of nonalcoholic fatty liver disease. Hepatology. 2023;77(5):1797-1835. PubMed
Cusi K, Orsak B, Bril F, et al. Long-term pioglitazone treatment for patients with nonalcoholic steatohepatitis and prediabetes or type 2 diabetes mellitus. Ann Intern Med. 2016;165(5):305-315. PubMed
Pioglitazone prescribing information. U.S. Food and Drug Administration. FDA Label
Resmetirom (Rezdiffra) prescribing information. U.S. Food and Drug Administration. FDA Label