Box Warning Research Articles

FDA Approval Summary: Teclistamab - A Bispecific CD3 T-cell Engager for Patients with Relapsed or Refractory Multiple Myeloma.

On October 25, 2022, the U.S. Food and Drug Administration (FDA) granted accelerated approval to teclistamab-cqyv (TECVAYLI; Janssen Biotech) for the treatment of adult patients with relapsed or refractory multiple myeloma who have received at least four prior lines of therapy, including a proteasome inhibitor, an immunomodulatory agent and an anti-CD38 monoclonal antibody. Substantial evidence of effectiveness was obtained from the MajesTEC-1 trial, a phase 1/2, single-arm, open-label, multi-center study. Patients received step-up doses of teclistamab at 0.06 mg/kg and 0.3 mg/kg followed by 1.5 mg/kg subcutaneously once weekly until disease progression or unacceptable toxicity. An overall response rate of 61.8% was observed, with a complete response or better rate of 28.2%. Cytokine release syndrome (CRS) occurred in 72% of patients and neurologic toxicity (NT) occurred in 57%, including immune effector cell-associated neurotoxicity syndrome (ICANS) in 6%. Due to the risk of CRS and NT, including ICANS, the U.S. prescribing information for teclistamab includes a boxed warning and teclistamab is available only through a restricted program under a risk evaluation and mitigation strategy. Here, we summarize the data and FDA review supporting the accelerated approval of teclistamab, a BCMA-directed bispecific antibody that was the first bispecific CD3 T-cell engager approved for treatment of multiple myeloma.

Presenting JAK inhibitor safety information to dermatology patients

AbstractJanus Kinase (JAK) inhibitors are treatment options for dermatologic conditions such as atopic dermatitis, psoriasis, vitiligo, and alopecia areata. Guidance on how to counsel patients on these novel treatments is limited. The purpose of this review is to provide options providers can use to discuss JAK inhibitors with dermatology patients. The PubMed database was searched for terms including “dermatology JAK inhibitor safety” and “presenting information to patients.” Relevant literature was selected for inclusion. Black box warnings were placed on JAK inhibitors after a large, controlled trial in rheumatoid arthritis patients did not prove that tofacitinib was as safe as tumor necrosis factor inhibitors; in clinical trials for dermatologic conditions, JAK inhibitors had low risks of serious adverse events. Patient barriers to comprehending treatment information include conflicting information and limited time for discussion of risks. To address these barriers, suggested approaches have included speaking in simple phrases, providing reliable sources, and offering educational materials appropriate for different cultures. When discussing risks, physicians may use anecdotes and frame risks and side effects in ways that decrease anxiety. JAK inhibitors have uncommon severe side effects and related concerns that may be hard for patients to overcome, even when benefits exceed risks. Standard educational approaches can be complemented by anecdotes and framing to help diminish patients' anxiety.

Intended And Unintended Outcomes After FDA Pediatric Antidepressant Warnings: A Systematic Review.

Since 2003, the Food and Drug Administration (FDA) has warned that antidepressants may be associated with suicidal thoughts and behaviors among youth. An FDA advisory in 2003 and a black-box warning in 2005 focused on children and adolescents younger than age eighteen. The FDA expanded the black-box warning in 2007 to include young adults. Both warnings were intended to increase physician monitoring of suicidal thoughts and behaviors. Our systematic review identified thirty-four studies of depression and suicide-related outcomes after these warnings; eleven of these studies met research design criteria established to reduce biases. The eleven studies examined monitoring for suicidal thoughts and behaviors, physician visits for depression, depression diagnoses, psychotherapy visits, antidepressant treatment and use, and psychotropic drug poisonings (a proxy for suicide attempts) and suicide deaths. We assessed possible spillover to adults not targeted by the warnings. The one study that measured intended physician monitoring of suicidal thoughts and behaviors did not find evidence of an increase. Multiple studies found significant unintended reductions in mental health care after the warnings. After these reductions, there were marked increases in psychotropic drug poisonings and suicide deaths. These findings support reevaluation of risks and benefits of the FDA's black-box antidepressant warnings.

The ABCs of JAKis: A Clinician's Guide to Safety and Monitoring of the Systemic JAK Inhibitors.

Janus kinase inhibitors (JAKis) have recently emerged in the arsenal of tools to treat dermatological conditions. However, there are some concerns regarding these treatments due to their boxed warning. Here we discuss the safe and effective use of JAKs for the treatment of a wide variety of dermatologic conditions. We will also discuss monitoring guidelines. J Drugs Dermatol. 2024;23(10):852-856. doi:10.36849/JDD.8073.

Direct oral anticoagulant approvals by four major regulatory agencies: a cross-sectional analysis of premarket and postmarket evidence

ObjectivesTo compare the premarket and postmarket evidence of safety and efficacy of direct oral anticoagulants approved for stroke prevention in atrial fibrillation patients across four major regulatory agencies.DesignCross-sectional.SettingEuropean Medicines Association...

JAK 1-3 inhibitors and TYK-2 inhibitors in dermatology: Practical pearls for the primary care physician

ABSTRACT Guidelines for primary care clinicians on monitoring and safety guidelines regarding Janus kinase and tyrosine kinase 2 inhibitors in the treatment of inflammatory skin conditions are often unclear. This review aims to provide the primary care physician with a review of clinically relevant and updated information regarding the monitoring and overall profile of these medications. To do so, a systematic review was conducted using the PubMed database and relevant Food and Drug Administration (FDA) approved drug inserts from manufacturers. Janus kinase and tyrosine kinase 2 inhibitors have recently gained FDA approval for the treatment of several inflammatory skin conditions including atopic dermatitis, plaque psoriasis, alopecia areata, and vitiligo. There is a known box warning associated with the Janus kinase inhibitors that create the need for monitoring and close follow-up while patients are undergoing these treatments. Although these medications are often prescribed by specialists, as their use becomes more prevalent and therapies continue to gain approval for the treatment of these commonly encountered conditions, it is important for the primary physician to be updated and aware of the current monitoring guidelines and safety profile for this class of medication. Both Janus kinase inhibitors and tyrosine kinase 2 inhibitors display significant efficacy in the treatment of their approved conditions and research continues to move forward with the approval of more medications from these classes.

Can CYP2C19 genotyping improve antiplatelet therapy efficacy in real-life practice? Recent advances.

Clopidogrel remains the most widely used P2Y₁₂ receptor inhibitor worldwide and is often used in combination with aspirin for secondary prevention in patients with arterial disease. The drug is associated with a wide response variability with one on three patients exhibiting little or no inhibition of adenosine diphosphate-induced platelet aggregation. It is a prodrug that is mainly metabolized by hepatic cytochrome P450 (CYP) 2C19. Patients who carry a CYP2C19 loss-of-function (LoF) allele have reduced metabolism of clopidogrel that is associated with reduced platelet inhibition compared to non-carriers that is associated with increased risk for thrombotic event occurrences, particularly, stent thrombosis. The United States Food and Drug Administration (US FDA) issued a black box warning in the clopidogrel label highlighting the importance of presence of CYP2C19 LOF allele during the insufficient metabolism of clopidogrel and availability of other potent P2Y₁₂ inhibitor for the treatment in CYP2C19 poor metabolizers. Clinical trials have conclusively demonstrated greater anti-ischemic benefits of prasugrel/ticagrelor in the treatment of patients carrying the CYP2C19 LoF allele. However, uniform use of these more potent P2Y₁₂ inhibitors has been associated with greater bleeding and cost, and lower adherence. The latter information provides a strong rationale for personalizing P2Y₁₂ inhibitor therapy based on the laboratory determination of CYP2C19 genotype. However, cardiologists have been slow to take up pharmacogenetic testing possibly due to lack of provider and patient education, clear cardiology guidelines and, and lack of positive results from adequately sized randomized clinical trials. However, current evidence strongly supports genotyping of patients who are candidates for clopidogrel. Physicians should strongly consider performing genetic tests to identify LoF carriers and treat these patients with more pharmacodynamically predictable P2Y₁₂ inhibitors than clopidogrel.

Post-marketing surveillance framework of cell and gene therapy products in the European Union, the United States, Japan, South Korea and China: a comparative study

BackgroundCell and gene therapy products (CGTPs) often receive accelerated approvals, lacking comprehensive long-term safety and efficacy data, which can raise significant safety concerns. This research aims to study the post-marketing surveillance (PMS) of CGTPs in the European Union (EU), the United States (US), Japan, South Korea, and China, to offer insights for the development of a secure and standardized post-marketing regulatory framework for CGTPs.MethodsRelated regulations and the implementation effect of PMS for approved CGTPs were studied searching PubMed, CNKI, and the official websites of the European Medicines Agency, the US Food and Drug Administration, Japan’s Pharmaceuticals and Medical Device Agency, South Korea’s Ministry of Food and Drug Safety, and the National Medical Products Administration of China.ResultsCompared to those in China, the guidelines of PMS for CGTPs in the EU, the US, Japan, and South Korea was more comprehensive. Notably, the EU had dedicated regulations and supporting guidelines of PMS. Of the 26 CGTPs approved in the EU, 88% were under additional monitoring, 38% received conditional marketing authorization, and 12% were authorized under exceptional circumstances, with 77% designated as orphan drugs. The US had released 34 guidelines specifically for CGTPs which, forming the foundation of post-marketing risk management. Among the 27 CGTPs approved in the US, 22% were required to perform risk evaluation and mitigation strategies, 37% added black box warnings in the package inserts, 63% mandated to post-marketing requirements, and 15% subject to post-marketing commitments. In Japan, stringent supervision measures encompassing all-case surveillance (79%) and re-examination (53%) were applied to the 19 approved CGTPs, with 21% approved through conditional and time-limited approval. The PMS for CGTPs in South Korea, mainly included PSUR, re-examination, and re-evaluation. China had introduced several relevant regulations, which consisted of general statements and lacked detailed guidance.ConclusionsThis study demonstrates that the regulatory policies of PMS for CGTPs in the EU, the US, Japan, and South Korea were comprehensive. The implementation of PMS for CGTPs in the EU, the US, and Japan was well developed. This knowledge holds valuable insights for China’s future learning and development in this field.

Risk factors that limit use of oral JAK inhibitors in chronic hand eczema: Findings from the Danish Skin Cohort

BackgroundOral Janus kinase inhibitors (JAKi) have black-box warnings of infections, cancer risk, cardiovascular and venous thromboembolic events. They may be used off-label for chronic hand eczema (CHE). ObjectivesAssess prevalence of risk factors potentially impacting oral JAKi safety in CHE patients. MethodsIn the Danish Skin Cohort, CHE patients were examined for risk factors affecting oral JAKi use at baseline and followed for 12 months. Data were collected through register linkage (e.g., cancer history) and through patient interviews (e.g., smoking habits). ResultsOf 941 adults with CHE (66.2% women; mean age 55.5 [standard deviation 13.3] years), 768 (81.6%) patients had at least one risk factor potentially impacting oral JAKi use, of which 682 (72.5%) had non-modifiable risk factors. Most common risk factors were current or former heavy smoking (62.8%, n=591), obesity (28.1%, n=264), hypercholesterolemia (21.5%, n=202), and hypertension (18.8%, n=177). Among patients without any risk factors at baseline (n=173), 20.2% (n=35) developed ≥1 risk factor during the following 12 months. LimitationsCertain risk factors may be underreported. ConclusionMost CHE patients have risk factors limiting appropriateness of oral JAKi use. Health care providers should assess risk factors in their patients when choosing treatment for CHE.

Clinical Evidence Supporting FDA Approval of Gene and RNA Therapies for Rare Inherited Conditions.

Gene and RNA therapies have potential to transform the treatment of rare inherited diseases, but there are concerns about the evidence supporting their use and high costs. We analyze the evidence supporting Food and Drug Administration (FDA) approval of gene and RNA therapies for rare inherited diseases and discuss implications for clinical practice and policy. We conducted a qualitative analysis of FDA documents outlining the basis of approval for gene and RNA therapies approved for rare inherited diseases between 2016 and 2023. For each drug, we gathered five characteristics of the evidence supporting FDA approval (no phase 3 trial, nonrandomized, no clinical endpoint, lack of demonstrated benefit, and significant protocol deviation) and four characteristics of the FDA approval process (prior rejection or complete response, negative committee vote, discrepancy between label and trial population, and boxed warning). The main outcome was the number of drugs with each characteristic. Between 2016 and 2023, 19 gene and RNA therapies received FDA approval to treat rare inherited diseases. The most common limitations in the evidence supporting approval of these drugs were nonrandomized studies (8/19, 42%), no clinical endpoint (7/19, 37%), lack of demonstrated benefit or inconsistent results (4/19, 21%), and no phase 3 trial (4/19, 21%). Half (3/6) of accelerated approvals and 57% (5/9) of drugs with breakthrough designation had nonrandomized trials, and gene therapies with one-time dosing were overrepresented (5/7, 71%) among the drugs with nonrandomized trials. Five of six accelerated approvals (83%) and five of nine pediatric drugs (56%), most of which were indicated for Duchenne muscular dystrophy, had no clinical endpoint. Four of nine (44%) pediatric drugs and four of six (67%) accelerated approvals failed to demonstrate benefit compared with none of the nonpediatric drugs and none of the traditional approvals. Five drugs, which all had different indications and represented a mix of RNA and gene therapies, did not have any of these evidence characteristics. Among drugs that received prior rejections or negative committee opinions, all four had nonrandomized trials and lacked a clinical endpoint, and 75% (3/4) lacked demonstrated benefit. Five of nine (56%) pediatric drugs were indicated for broader age groups according to the drug label compared with the trial populations. Of the three drugs with boxed warnings, two had pediatric indications and nonrandomized studies, and one had no phase 3 trial. Issues related to trial design, outcome, and data integrity in the evidence supporting FDA approval of rare inherited disease gene and RNA therapies raise questions about whether this evidence is adequate to inform prescribing decisions. Gene and RNA therapies with accelerated approval and pediatric indications were overrepresented among drugs lacking clinical endpoints or demonstrated benefit and should be the focus of efforts to reduce uncertainty in the evidence.

Ambrisentan prescribing increase after removal of boxed warning

Ambrisentan prescribing increase after removal of boxed warning

PI3K Inhibitors in Hematology: When One Door Closes….

The PI3K signaling pathway regulates key cellular processes and is one of the most aberrantly activated pathways in cancer. The class I PI3K catalytic subunits p110γ and p110δ are highly enriched in leukocytes, providing an additional rationale for targeting these PI3Ks in hematologic malignancies. In 2014, the PI3Kδ inhibitor idelalisib was the first of four PI3K inhibitors (PI3Ki) to receive regulatory approval for relapsed B-cell malignancies. This was followed by approvals of the pan-class I inhibitor copanlisib (2017), the dual PI3Kγ/δ inhibitor duvelisib (2018), and the PI3Kδ and casein kinase 1ε inhibitor umbralisib (2021). Copanlisib and umbralisib received accelerated approvals, whereas idelalisib and duvelisib received initial accelerated approvals followed by full approvals. The accelerated approvals were based on overall response rates; however, follow-up studies showed increased risk of death and serious side effects. Furthermore, the confirmatory trial with copanlisib failed to show an improvement in progression-free survival when compared with chemoimmunotherapy. These developments led to black box warnings for idelalisib and duvelisib and withdrawal of copanlisib and umbralisib from the market by their manufacturers. Given the uncertain future of this drug class, additional manufacturers terminated ongoing phase III trials with novel PI3Kis. In this study, we review the development and current status of PI3Kis in hematology, limitations to their use, and our perspective on whether there is a future for PI3Kis in hematology.

Removing the FDA’s Boxed Hepatotoxicity Warning and Liver Function Testing Requirement for Ambrisentan

Endothelin receptor antagonists are first-line therapy for pulmonary arterial hypertension (PAH). The first 2 agents approved in the class, bosentan and ambrisentan, initially carried boxed warnings for hepatotoxicity and required monthly liver function tests (LFTs) as part of a risk evaluation and mitigation strategy (REMS); however, in 2011, as further safety data emerged on ambrisentan, the boxed hepatotoxicity warning and LFT requirements were removed. To analyze changes in the use of and LFT monitoring for ambrisentan and bosentan after changes to the ambrisentan labeling and REMS. This serial cross-sectional study used data from 3 longitudinal health care insurance claims databases-Medicaid, Optum's deidentified Clinformatics Data Mart, and Merative Marketscan-to perform an interrupted time series analysis of prescription fills and LFTs for patients taking ambrisentan and bosentan. Participants were patients filling prescriptions for ambrisentan and bosentan from July 1, 2007, to December 31, 2018. Data analysis was performed from April 2021 to August 2023. Removal of the boxed warning for hepatotoxicity and the REMS LFT monitoring requirements on ambrisentan in March 2011. The primary outcomes were use of ambrisentan (ie, individuals with at least 1 dispensing per 1 000 000 individuals enrolled in the 3 datasets) vs bosentan and LFT monitoring (ie, proportion of initiators with at least 1 ordered test) before initiation and before the first refill. A total of 10 261 patients received a prescription for ambrisentan during the study period (7442 women [72.5%]; mean [SD] age, 52.6 [17.6] years), and 11 159 patients received a prescription for bosentan (7931 women [71.1%]; mean [SD] age, 47.7 [23.7] years). Removal of the ambrisentan boxed hepatotoxicity warning and LFT monitoring requirement was associated with an immediate increase in the use of ambrisentan (1.50 patients per million enrollees; 95% CI, 1.08 to 1.92 patients per million enrollees) but no significant change in the use of bosentan. There were reductions in recorded LFTs before drug initiation (13.1% absolute decrease; 95% CI, -18.2% to -8.0%) and before the first refill (26.4% absolute decrease; 95% CI, -34.4% to -18.5%) of ambrisentan but not bosentan. In this serial cross-sectional study of ambrisentan, labeling changes and removal of the REMS-related LFT requirement were associated with shifts in prescribing and testing behavior for ambrisentan but not bosentan. Further clinician education may be needed to maximize the benefits of REMS programs and labeling warnings designed to ensure the safe administration of high-risk medications.

Fluoroquinolones in Focus: Unraveling Prescription Trends among Clinician Specialties in Washington State

Background: An overall decrease of prescriptions for outpatient fluoroquinolones (FQs) following the FDA’s release of boxed warnings in 2016 was shown in a previous analysis1. An additional study found that this decline held true when further broken down by specialty 2. We sought to determine which different clinician specialties in Washington State (WA) continue to prescribe FQs and if these rates are congruent with previously conducted national analyses. Methods: We conducted a comprehensive analysis of Medicare Part D data from 2021. We identified specialty types contributing the highest proportions of FQ claims from the total volume of claims in 2021. Subsequently, we calculated the average FQ claims per 1,000 Medicare Part D beneficiaries for each specialty. The analysis excluded providers with missing beneficiary data. All dosage formulations were included (i.e. topical & oral). We repeated this process for each year from 2021 to 2013 to assess changes in the average FQ prescription rate for each specialty over time. Results: Our analysis encompassed 99,250 FQ prescriptions involving 976,209 Medicare Part D beneficiaries from January 1 to December 30, 2021. Among the specialties, urologists emerged as the highest prescribers of FQs to Medicare Part D beneficiaries, closely followed by ophthalmologists and family practitioners (Table 1). Notably, 72.4% of urologists prescribed FQs, while only 12.4% of family practitioners did so in 2021. Trend analysis indicated that the average FQ claims per 1,000 beneficiaries for urologists decreased from 251 claims per 1,000 beneficiaries (SD = 177.98) in 2013 to 130 claims per 1,000 beneficiaries (SD = 122.50) in 2021 (Figure 1A). In contrast, the only specialty types that had positive trends in average FQ claims per 1,000 beneficiaries from 2013 to 2021 included ophthalmologists, optometrists, and otolaryngologists (Figure 1A). Conclusion: Throughout the years leading up to 2021, most prescriber specialties contributing high volumes of FQ claims experienced a decline in FQ prescriptions. The positive trend noted amongst ophthalmologists, optometrists, and otolaryngologists could be due to the limited ability to differentiate between oral & topical FQ formulations within the dataset. These findings underscore the importance of understanding specialist prescribing behaviors and partnering with them to formulate tailored antibiotic stewardship guidance. By doing so, we can further promote patient safety and well-being in the context of FQ usage. Public health departments can promote more holistic antibiotic stewardship interventions and better patient safety outcomes with FQs. Ambulatory Fluoroquinolone Use in the United States 2015–2019 Outpatient Fluoroquinolone Prescription Fills.Disclosure: Erica Stohs: Contracted research - Merck; Contracted research – bioMerieux

Will Black Box Warning Affect Development of CAR-T Therapy

Cell therapy has emerged as an approved treatment and has saved many patients. As a living therapy, it serves as a role model for advancements in biology, especially in combating cancer to some extent. Despite the progress in cell therapy, one of the biggest issues on the regulatory side is that the FDA now requires a black box warning for the six cell therapies currently on the market. This announcement was nd made on January 22 2024, mandating producers to remind users about the risk of developing lymphoma. To date, all companies have put the black box warning in their product sheet. After the announcement, there was a rapid change in the stock market for related companies. However, based on our analysis, there is no need to overreact to such regulatory changes.

A case of severe anaphylactic reaction after administration of diagnostic-dose ferumoxytol in a pediatric patient

We describe a case of anaphylaxis during administration of intravenous (IV) ferumoxytol as a magnetic resonance imaging (MRI) contrast agent in a 4-year-old patient with complicated past medical history including YARS genetic mutation with resultant liver failure and deceased donor liver transplantation, stage IV chronic kidney disease (CKD), and hypertension. The patient was noted to have labored breathing 4 min after initiation of ferumoxytol infusion and was subsequently rapidly intubated and returned to the intensive care unit (ICU) for monitoring. Anaphylactic reactions to therapeutic doses of ferumoxytol led to issuance of a black box warning by the FDA in 2015. Adverse reactions to lower-dose ferumoxytol used in diagnostic imaging, however, are rare and there has been a paucity of documented anaphylactic reactions in the literature.

Microfluidic human physiomimetic liver model as a screening platform for drug induced liver injury

The pre-clinical animal models often fail to predict intrinsic and idiosyncratic drug induced liver injury (DILI), thus contributing to drug failures in clinical trials, black box warnings and withdrawal of marketed drugs. This suggests a critical need for human-relevant in vitro models to predict diverse DILI phenotypes. In this study, a porcine liver extracellular matrix (ECM) based biomaterial ink with high printing fidelity, biocompatibility and tunable rheological and mechanical properties is formulated for supporting both parenchymal and non-parenchymal cells. Further, we applied 3D printing and microfluidic technology to bioengineer a human physiomimetic liver acinus model (HPLAM), recapitulating the radial hepatic cord-like structure with functional sinusoidal microvasculature network, biochemical and biophysical properties of native liver acinus. Intriguingly, the human derived hepatic cells incorporated HPLAM cultured under physiologically relevant microenvironment, acts as metabolic biofactories manifesting enhanced hepatic functionality, secretome levels and biomarkers expression over several weeks. We also report that the matured HPLAM reproduces dose- and time-dependent hepatotoxic response of human clinical relevance to drugs typically recognized for inducing diverse DILI phenotypes as compared to conventional static culture. Overall, the developed HPLAM emulates in vivo like functions and may provide a useful platform for DILI risk assessment to better determine safety and human risk.

Black boxed warnings on montelukast-related neuropsychiatric reactions

Black boxed warnings on montelukast-related neuropsychiatric reactions

Plastic Surgeons' Perspective on the FDA Breast Implant Regulatory Mandates.

In 2021, the US FDA issued a new checklist, labeling, and rupture-screening recommendations for breast implants to improve the decision-making process. The aim of this study was to understand plastic surgeons' perspective on these changes and their perceived impact on clinical practice. In September 2023, a 27-question multiple-choice cross-sectional survey was distributed to 4352 active members of the American Society of Plastic Surgeons to evaluate attitudes on the FDA's black-box warning, informed decision checklist, and updated rupture-screening recommendations. A total of 591 responses were collected (13.6%). The majority of respondents were between the ages of 45 and 64 years (58%) and had been in practice for more than 20 years (52%). Surgeons felt that some additions were appropriate; however, the majority (57%) stated that the informed decision checklist did not have a positive impact on workflow; 66% were also neutral or disagreed with the reported incidence rates related to complications and cancer. Nearly half of respondents (47%) did not feel the black-box warning improved their patients' understanding of the risks and benefits. Additionally, 47% of respondents also believed these requirements, in combination, did not improve the overall patient experience with implants. Respondents had an overall positive response towards the addition of risk information provided by the FDA-issued guidance and updates to rupture-screening recommendations. However, they remained divided as to whether the black-box warning and patient decision checklist had an overall positive impact on clinical practice patterns.

Drug-induced impairment of mitochondrial fatty acid oxidation and steatosis: assessment of causal relationship with 45 pharmaceuticals.

Drug-induced liver injury (DILI) represents a major issue for pharmaceutical companies, being a potential cause of black-box warnings on marketed pharmaceuticals, or drug withdrawal from the market. Lipid accumulation in the liver also referred to as steatosis, may be secondary to impaired mitochondrial fatty acid oxidation (mtFAO). However, an overall causal relationship between drug-induced mtFAO inhibition and the occurrence of steatosis in patients has not yet been established with a high number of pharmaceuticals. Hence, 32 steatogenic and 13 nonsteatogenic drugs were tested for their ability to inhibit mtFAO in isolated mouse liver mitochondria. To this end, mitochondrial respiration was measured with palmitoyl-l-carnitine, palmitoyl-CoA + l-carnitine, or octanoyl- l-carnitine. This mtFAO tri-parametric assay was able to predict the occurrence of steatosis in patients with a sensitivity and positive predictive value above 88%. To get further information regarding the mechanism of drug-induced mtFAO impairment, mitochondrial respiration was also measured with malate/glutamate or succinate. Drugs such as diclofenac, methotrexate, and troglitazone could inhibit mtFAO secondary to an impairment of the mitochondrial respiratory chain, whereas dexamethasone, olanzapine, and zidovudine appeared to impair mtFAO directly. Mitochondrial swelling, transmembrane potential, and production of reactive oxygen species were also assessed for all compounds. Only the steatogenic drugs amiodarone, ketoconazole, lovastatin, and toremifene altered all these 3 mitochondrial parameters. In conclusion, our tri-parametric mtFAO assay could be useful in predicting the occurrence of steatosis in patients. The combination of this assay with other mitochondrial parameters could also help to better understand the mechanism of drug-induced mtFAO inhibition.