Efficacy and Safety of 5-Day Oral Ensitrelvir for Patients With Mild to Moderate COVID-19: The SCORPIO-SR Randomized Clinical Trial

Importance

Treatment options for COVID-19 are warranted irrespective of the presence of risk factors for severe disease.

Objective

To assess the efficacy and safety of ensitrelvir in patients with mild to moderate COVID-19.

Design, Setting, and Participants

This phase 3 part of a phase 2/3, double-blind, placebo-controlled randomized clinical trial was conducted from February 10 to July 10, 2022, with a 28-day follow-up period, at 92 institutions in Japan, Vietnam, and South Korea. Patients (aged 12 to <70 years) with mild to moderate COVID-19 within 120 hours of positive viral test results were studied.

Interventions

Patients were randomized (1:1:1) to receive 125 mg of once-daily ensitrelvir (375 mg on day 1), 250 mg of once-daily ensitrelvir (750 mg on day 1), or placebo for 5 days.

Main Outcomes and Measures

The primary end point was the time to resolution of the composite of 5 characteristic symptoms of SARS-CoV-2 Omicron infection, assessed using a Peto-Prentice generalized Wilcoxon test stratified by vaccination history. Virologic efficacy and safety were also assessed.

Results

A total of 1821 patients were randomized, of whom 1030 (347 in the 125-mg ensitrelvir group, 340 in the 250-mg ensitrelvir group, and 343 in the placebo group) were randomized in less than 72 hours of disease onset (primary analysis population). The mean (SD) age in this population was 35.2 (12.3) years, and 552 (53.6%) were men. A significant difference was observed between the 125-mg ensitrelvir group and the placebo group (P = .04 with a Peto-Prentice generalized Wilcoxon test). The difference in median time was approximately 1 day between the 125-mg ensitrelvir group and the placebo group (167.9 vs 192.2 hours; difference, -24.3 hours; 95% CI, -78.7 to 11.7 hours). Adverse events were observed in 267 of 604 patients (44.2%) in the 125-mg ensitrelvir group, 321 of 599 patients (53.6%) in the 250-mg ensitrelvir group, and 150 of 605 patients (24.8%) in the placebo group, which included a decrease in high-density lipoprotein level (188 [31.1%] in the 125-mg ensitrelvir group, 231 [38.6%] in the 250-mg ensitrelvir group, and 23 [3.8%] in the placebo group). No treatment-related serious adverse events were reported.

Conclusions and Relevance

In this randomized clinical trial, 125-mg ensitrelvir treatment reduced the time to resolution of the 5 typical COVID-19 symptoms compared with placebo in patients treated in less than 72 hours of disease onset; the absolute difference in median time to resolution was approximately 1 day. Ensitrelvir demonstrated clinical and antiviral efficacy without new safety concerns. Generalizability to populations outside Asia should be confirmed.

Trial Registration

Japan Registry of Clinical Trials Identifier: jRCT2031210350.

A phase 2/3 study of S-217622 in participants with SARS-CoV-2 infection (Phase 3 part)

BACKGROUND

Limited treatment options exist for patients with mild-to-moderate coronavirus disease 2019 (COVID-19), irrespective of vaccination history or risk status. Ensitrelvir is a novel oral severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) 3C-like (3CL) protease inhibitor. While phase 2 studies of ensitrelvir have demonstrated promising results in treating mild-to-moderate COVID-19, evaluation of its clinical efficacy due to shifting vaccination status and emergence of the Omicron variant represents significant challenges. Here, we describe the protocol for a phase 3 study designed to evaluate the efficacy and safety of ensitrelvir in patients with mild-to-moderate COVID-19, regardless of risk status or vaccination history.

METHODS

This is a multicenter, randomized, double-blind, placebo-controlled, phase 3 study. Patients with mild-to-moderate COVID-19 within 120 hours from onset will be randomized in a 1:1:1 ratio into 3 treatment arms-ensitrelvir 125 mg (375 mg loading dose on Day 1), ensitrelvir 250 mg (750 mg loading dose on Day 1), and placebo. The study interventions will be administered orally, once-daily, for 5 days. The primary endpoint will be the time to resolution of 5 symptoms of COVID-19 (stuffy or runny nose, sore throat, cough, feeling hot or feverish, and low energy or tiredness), and the key secondary endpoints will include the change from baseline on Day 4 in the amount of SARS-CoV-2 viral ribonucleic acid (RNA) and the time to first negative SARS-CoV-2 viral titer. The primary population for the primary and key secondary endpoints will be patients with <72 hours from COVID-19 onset to randomization and, subsequently, patients in entire patient population (<120 hours) in the ensitrelvir 125 mg group. Closed testing procedure will be used for the primary and key secondary endpoints in both the primary and entire patient populations. All safety assessments and adverse events (AE) will be reported.

DISCUSSION

In a post hoc analysis of the phase 2b study, compared with placebo, ensitrelvir demonstrated a reduced time to resolution of 5 symptoms in patients with mild-to-moderate COVID-19. Through this study, we intend to validate and establish the efficacy and safety of ensitrelvir in patients with mild-to-moderate COVID-19.

S-217622, a SARS-CoV-2 main protease inhibitor, decreases viral load and ameliorates COVID-19 severity in hamsters

In parallel with vaccination, oral antiviral agents are highly anticipated to act as countermeasures for the treatment of the coronavirus disease 2019 (COVID-19) pandemic caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Oral antiviral medication demands not only high antiviral activity but also target specificity, favorable oral bioavailability, and high metabolic stability. Although a large number of compounds have been identified as potential inhibitors of SARS-CoV-2 infection in vitro, few have proven to be effective in vivo. Here, we show that oral administration of S-217622 (ensitrelvir), an inhibitor of SARS-CoV-2 main protease (M^pro; also known as 3C-like protease), decreases viral load and ameliorates disease severity in SARS-CoV-2-infected hamsters. S-217622 inhibited viral proliferation at low nanomolar to submicromolar concentrations in cells. Oral administration of S-217622 demonstrated favorable pharmacokinetic properties and accelerated recovery from acute SARS-CoV-2 infection in hamster recipients. Moreover, S-217622 exerted antiviral activity against SARS-CoV-2 variants of concern, including the highly pathogenic Delta variant and the recently emerged Omicron BA.5 and BA.2.75 variants. Overall, our study provides evidence that S-217622, an antiviral agent that is under evaluation in a phase 3 clinical trial (clinical trial registration no. jRCT2031210350), has remarkable antiviral potency and efficacy against SARS-CoV-2 and is a prospective oral therapeutic option for COVID-19.

1133. Investigation of Treatment-Emergent Amino Acid Substitutions in Nonstructural Protein 5 from Ph2a Study of Ensitrelvir, a Novel Oral SARS-CoV-2 3C-Like Protease Inhibitor

Background

Ensitrelvir is a novel oral SARS-CoV-2 3C-like protease inhibitor, and under late clinical development stage for COVID-19 disease. In Ph2a and Ph2b studies, ensitrelvir demonstrated rapid decline of viral titer and viral RNA compared with placebo, and tolerability. To investigate treatment-emergent amino acid substitutions (TEAASs), we analyzed viral RNA sequences of nonstructural protein 5 (NSP5), target of ensitrelvir from Ph2a study in Japan.

Methods

In Ph2a study, 69 patients with confirmed SARS-CoV-2 infection were randomized 1:1:1 to ensitrelvir with the loading dose on Day 1/maintenance dose on Day 2-5 (375/125 mg or 750/250 mg), or placebo. Intent-to-treat (ITT) population was defined as participants confirmed with positivity by qualitative RT-PCR at baseline. TEAASs were defined as novel amino acid substitutions identified after treatment with ensitrelvir. NSP5 sequence analysis was performed with sanger sequencing using nasopharyngeal swab samples at Day 1, 6, 9, 14, and 21 with allowances from ITT population with ensitrelvir. Infectious viral titer was measured by virus-induced cytopathic effects in VeroE6/TMPRSS2 cells. Viral RNA was quantified by RT-PCR.

Results

By NSP5 sequence analysis, TEAASs were observed in 1 patient from 375/125 mg group and 2 patients from 750/250 mg group. H246Y in 375/125 mg was detected from specimen on Day 8, and A234S and T198I in 750/250 mg were detected from specimens on Day 8 and Day 14, respectively. Structural analysis revealed that these mutations are located outside of the active center of 3C-like protease which is the binding site of ensitrelvir. Viral titer and viral RNA in each specimen, in which TEAASs were observed, were below lower limit of detection and lower limit of quantification, respectively. Furthermore, H246Y, A234S and T198I are rare substitution (&lt; 0.05%) among SARS-CoV-2 variants according to Global Initiative on Sharing Avian Influenza Data.

Conclusion

In Ph2a study, H246Y, A234S, and T198I in NSP5 were detected as TEAASs. However, results of viral titer and viral RNA, and structural information suggest that these mutations do not have the impact on antiviral efficacy of ensitrelvir.

Disclosures

All Authors: No reported disclosures.

Efficacy and safety of ensitrelvir in patients with mild-to-moderate COVID-19: the phase 2b part of a randomized, placebo-controlled, phase 2/3 study

Background

This phase 2b part of a randomized phase 2/3 study assessed the efficacy and safety of ensitrelvir for mild-to-moderate coronavirus disease 2019 (COVID-19) during the Omicron epidemic.

Methods

Patients were randomized (1:1:1) to orally receive ensitrelvir fumaric acid 125 mg (375 mg on day 1) or 250 mg (750 mg on day 1) or placebo once daily for 5 days. The co-primary endpoints were the change from baseline in the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) titer on day 4 and time-weighted average change from baseline up to 120 hours in the total score of predefined 12 COVID-19 symptoms. Safety was assessed through adverse events.

Results

A total of 341 patients (ensitrelvir 125 mg group, 114; ensitrelvir 250 mg group, 116; and placebo group, 111; male, 53.5%–64.9%; mean age, 35.3–37.3 years) were included in the efficacy analyses. The change from baseline in the SARS-CoV-2 titer on day 4 was significantly greater with both ensitrelvir doses than with placebo (differences from placebo: -0.41 log10 50% tissue-culture infectious dose/mL, P &lt; 0.0001 for both). The total score of the 12 COVID-19 symptoms did not show a significant difference between the ensitrelvir groups and placebo group. The time-weighted average change from baseline up to 120 hours was significantly greater with ensitrelvir versus placebo in several subtotal scores, including acute symptoms and respiratory symptoms. Most adverse events were mild in severity.

Conclusions

Ensitrelvir treatment demonstrated a favorable antiviral efficacy and potential clinical benefit with an acceptable safety profile.

Efficacy of ensitrelvir against SARS-CoV-2 in a delayed-treatment mouse model

Objectives

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is the aetiological agent of coronavirus disease 2019 (COVID-19) and a devastating worldwide health concern. Development of safe and effective treatments is not only important for interventions during the current pandemic, but also for providing general treatment options moving forward. We have developed ensitrelvir, an antiviral compound that targets the 3C-like protease of SARS-CoV-2. In this study, a delayed-treatment mouse model was used to clarify the potential in vivo efficacy of ensitrelvir.

Methods

Female BALB/cAJcl mice of different ages were infected with the SARS-CoV-2 gamma strain (hCoV-19/Japan/TY7-501/2021) or mouse-adapted SARS-CoV-2 MA-P10 and then 24 h post-infection orally administered various doses of ensitrelvir or vehicle. Viral titres and RNA levels in the lungs were quantified using VeroE6/TMPRSS2 cells and RT–qPCR, respectively. Body weight loss, survival, lung weight, cytokine/chemokine production, nucleocapsid protein expression and lung pathology were evaluated to investigate the in vivo efficacy of ensitrelvir.

Results

Based on infectious viral titres and viral RNA levels in the lungs of infected mice, ensitrelvir reduced viral loads in a dose-dependent manner. The antiviral efficacy correlated with increased survival, reduced body weight loss, reduced pulmonary lesions and suppression of inflammatory cytokine/chemokine levels.

Conclusions

This was the first evaluation of the in vivo anti-SARS-CoV-2 efficacy of ensitrelvir in a delayed-treatment mouse model. In this model, ensitrelvir demonstrated high antiviral potential and suppressed lung inflammation and lethality caused by SARS-CoV-2 infection. The findings support the continued clinical development of ensitrelvir as an antiviral agent to treat patients with COVID-19.

Discovery of S-217622, a Noncovalent Oral SARS-CoV-2 3CL Protease Inhibitor Clinical Candidate for Treating COVID-19

The coronavirus disease 2019 (COVID-19) pandemic, caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), has resulted in millions of deaths and threatens public health and safety. Despite the rapid global spread of COVID-19 vaccines, effective oral antiviral drugs are urgently needed. Here, we describe the discovery of S-217622, the first oral noncovalent, nonpeptidic SARS-CoV-2 3CL protease inhibitor clinical candidate. S-217622 was discovered via virtual screening followed by biological screening of an in-house compound library, and optimization of the hit compound using a structure-based drug design strategy. S-217622 exhibited antiviral activity in vitro against current outbreaking SARS-CoV-2 variants and showed favorable pharmacokinetic profiles in vivo for once-daily oral dosing. Furthermore, S-217622 dose-dependently inhibited intrapulmonary replication of SARS-CoV-2 in mice, indicating that this novel noncovalent inhibitor could be a potential oral agent for treating COVID-19.

Characterization of the In Vitro and In Vivo Efficacy of Baloxavir Marboxil against H5 Highly Pathogenic Avian Influenza Virus Infection

Human infections caused by the H5 highly pathogenic avian influenza virus (HPAIV) sporadically threaten public health. The susceptibility of HPAIVs to baloxavir acid (BXA), a new class of inhibitors for the influenza virus cap-dependent endonuclease, has been confirmed in vitro, but it has not yet been fully characterized. Here, the efficacy of BXA against HPAIVs, including recent H5N8 variants, was assessed in vitro. The antiviral efficacy of baloxavir marboxil (BXM) in H5N1 virus-infected mice was also investigated. BXA exhibited similar in vitro activities against H5N1, H5N6, and H5N8 variants tested in comparison with seasonal and other zoonotic strains. Compared with oseltamivir phosphate (OSP), BXM monotherapy in mice infected with the H5N1 HPAIV clinical isolate, the A/Hong Kong/483/1997 strain, also caused a significant reduction in viral titers in the lungs, brains, and kidneys, thereby preventing acute lung inflammation and reducing mortality. Furthermore, compared with BXM or OSP monotherapy, combination treatments with BXM and OSP using a 48-h delayed treatment model showed a more potent effect on viral replication in the organs, accompanied by improved survival. In conclusion, BXM has a potent antiviral efficacy against H5 HPAIV infections.

Acsl1 is essential for skin barrier function through the activation of linoleic acid and biosynthesis of ω-O-acylceramide in mice

The long-chain acyl-CoA synthase1 (Acsl1) is a major enzyme that converts long-chain fatty acids to acyl-CoAs. The role of Acsl1 in energy metabolism has been elucidated in the adipose tissue, heart, and skeletal muscle. Here, we demonstrate that systemic deficiency of Acsl1 caused severe skin barrier defects, leading to embryonic lethality. Acsl1 mRNA and protein are expressed in the Acsl1^+/+ epidermis, which are absent in Acsl1^-/- mice. In Acsl1^-/- mice, epidermal ceramide [EOS] (Cer[EOS]) containing ω-O-esterified linoleic acid, a lipid essential for the skin barrier, was significantly reduced. Conversely, ω-hydroxy ceramide (Cer[OS]), a precursor of Cer[EOS], was increased. Moreover, the levels of triglyceride (TG) species containing linoleic acids were lower in Acsl1^-/- mice, whereas those not containing linoleic acid were comparable to Acsl1^+/+ mice. As TG is considered to work as a reservoir of linoleic acid for the biosynthesis of Cer[EOS] from Cer[OS], our results suggest that Acsl1 plays an essential role in ω-O-acylceramide synthesis by providing linoleic acid for ω-O-esterification. Therefore, our findings identified a new biological role of Acsl1 as a regulator of the skin barrier.

Air-liquid interphase culture confers SARS-CoV-2 susceptibility to A549 alveolar epithelial cells

The human lung cell A549 is susceptible to infection with a number of respiratory viruses. However, A549 cells are resistant to Severe Acute Respiratory Syndrome-Coronavirus-2 (SARS-CoV-2) infection in conventional submerged culture, and this would appear to be due to low expression levels of the SARS-CoV-2 entry receptor: angiotensin-converting enzyme-2 (ACE2). Here, we examined SARS-CoV-2 susceptibility to A549 cells after adaptation to air-liquid interface (ALI) culture. A549 cells in ALI culture yielded a layer of mucus on their apical surface, exhibited decreased expression levels of the proliferation marker KI-67 and intriguingly became susceptible to SARS-CoV-2 infection. We found that A549 cells increased the endogenous expression levels of ACE2 and TMPRSS2 following adaptation to ALI culture conditions. Camostat, a TMPRSS2 inhibitor, reduced SARS-CoV-2 infection in ALI-cultured A549 cells. These findings indicate that ALI culture switches the phenotype of A549 cells from resistance to susceptibility to SARS-CoV-2 infection through upregulation of ACE2 and TMPRSS2.

5-Hydroxymethyltubercidin exhibits potent antiviral activity against flaviviruses and coronaviruses, including SARS-CoV-2

Newly emerging or re-emerging viral infections continue to cause significant morbidity and mortality every year worldwide, resulting in serious effects on both health and the global economy. Despite significant drug discovery research against dengue viruses (DENVs) and severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2), no fully effective and specific drugs directed against these viruses have been discovered. Here, we examined the anti-DENV activity of tubercidin derivatives from a compound library from Hokkaido University and demonstrated that 5-hydroxymethyltubercidin (HMTU, HUP1108) possessed both potent anti-flavivirus and anti-coronavirus activities at submicromolar levels without significant cytotoxicity. Furthermore, HMTU inhibited viral RNA replication and specifically inhibited replication at the late stages of the SARS-CoV-2 infection process. Finally, we demonstrated that HMTU 5′-triphosphate inhibited RNA extension catalyzed by the viral RNA-dependent RNA polymerase. Our findings suggest that HMTU has the potential of serving as a lead compound for the development of a broad spectrum of antiviral agents, including SARS-CoV-2.

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We identified tubercidin derivatives as broad-spectrum antiviral compounds

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HMTU exhibited potent antiviral activity against flaviviruses and coronaviruses

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HMTU specifically inhibited replication at a late stage of the viral infection process

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HMTU 5′-triphosphate inhibited RNA extension catalyzed by viral RdRp

TMPRSS11D and TMPRSS13 Activate the SARS-CoV-2 Spike Protein

Severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) utilizes host proteases, including a plasma membrane-associated transmembrane protease, serine 2 (TMPRSS2) to cleave and activate the virus spike protein to facilitate cellular entry. Although TMPRSS2 is a well-characterized type II transmembrane serine protease (TTSP), the role of other TTSPs on the replication of SARS-CoV-2 remains to be elucidated. Here, we have screened 12 TTSPs using human angiotensin-converting enzyme 2-expressing HEK293T (293T-ACE2) cells and Vero E6 cells and demonstrated that exogenous expression of TMPRSS11D and TMPRSS13 enhanced cellular uptake and subsequent replication of SARS-CoV-2. In addition, SARS-CoV-1 and SARS-CoV-2 share the same TTSPs in the viral entry process. Our study demonstrates the impact of host TTSPs on infection of SARS-CoV-2, which may have implications for cell and tissue tropism, for pathogenicity, and potentially for vaccine development.

SARS-CoV-2 variants with mutations at the S1/S2 cleavage site are generated in vitro during propagation in TMPRSS2-deficient cells

The spike (S) protein of Severe Acute Respiratory Syndrome-Coronavirus-2 (SARS-CoV-2) binds to a host cell receptor which facilitates viral entry. A polybasic motif detected at the cleavage site of the S protein has been shown to broaden the cell tropism and transmissibility of the virus. Here we examine the properties of SARS-CoV-2 variants with mutations at the S protein cleavage site that undergo inefficient proteolytic cleavage. Virus variants with S gene mutations generated smaller plaques and exhibited a more limited range of cell tropism compared to the wild-type strain. These alterations were shown to result from their inability to utilize the entry pathway involving direct fusion mediated by the host type II transmembrane serine protease, TMPRSS2. Notably, viruses with S gene mutations emerged rapidly and became the dominant SARS-CoV-2 variants in TMPRSS2-deficient cells including Vero cells. Our study demonstrated that the S protein polybasic cleavage motif is a critical factor underlying SARS-CoV-2 entry and cell tropism. As such, researchers should be alert to the possibility of de novo S gene mutations emerging in tissue-culture propagated virus strains.

Inhibition of dengue virus infection by 1-stearoyl-2-arachidonoyl-phosphatidylinositol in vitro

Dengue fever is an acute febrile infectious disease caused by dengue virus (DENV). Despite the significant public health concerns posed by DENV, there are currently no effective anti-DENV therapeutic agents. To develop such drugs, a better understanding of the detailed mechanisms of DENV infection is needed. Both lipid metabolism and lipid synthesis are activated in DENV-infected cells, so we used lipid screening to identify potential antiviral lipid molecules. We identified 1-stearoyl-2-arachidonoyl-phosphatidylinositol (SAPI), which is the most abundant endogenous phosphatidylinositol (PI) molecular species, as an anti-DENV lipid molecule. SAPI suppressed the cytopathic effects induced by DENV2 infection as well as the replication of all DENV serotypes without inhibiting the entry of DENV2 into host cells. However, no other PI molecular species or PI metabolites, including lysophosphatidylinositols and phosphoinositides, displayed anti-DENV2 activity. Furthermore, SAPI suppressed the production of DENV2 infection-induced cytokines and chemokines, including C-C motif chemokine ligand (CCL)5, CCL20, C-X-C chemokine ligand 8, IL-6, and IFN-β. SAPI also suppressed the TNF-α production induced by LPS stimulation in macrophage cells differentiated from THP-1 cells. Our results demonstrated that SAPI is an endogenous inhibitor of DENV and modulated inflammatory responses in DENV2-infected cells, at least in part via TLR 4.-Sanaki, T., Wakabayashi, M., Yoshioka, T., Yoshida, R., Shishido, T., Hall, W. W., Sawa, H., Sato, A. Inhibition of dengue virus infection by 1-stearoyl-2-arachidonoyl-phosphatidylinositol in vitro.

Possible roles of long-chain sphingomyelines and sphingomyelin synthase 2 in mouse macrophage inflammatory response

To evaluate the precise role of sphingomyelin synthase 2 (SMS2) in sphingomyelin (SM) metabolism and their anti-inflammatory properties, we analyzed species of major SM and ceramide (Cer) (18:1, 18:0 sphingoid backbone, C14 - C26 N-acyl part) in SMS2 knockout and wild-type mouse plasma and liver using HPLC-MS. SMS2 deficiency significantly decreased very long chain SM (SM (d18:1/22:0) and SM (d18:1/24:0 or d18:0/24:1)) and increased very long chain Cer (Cer (d18:1/24:0 or d18:0/24:1) and Cer (d18:1/24:1)), but not long chain SM (SM (d18:1/16:0), SM (d18:1/18:0 or d18:0/18:1) and SM (d18:1/18:1)) in plasma. To examine the effects of SM on inflammation, we studied the role of very long chain SM in macrophage activation. Addition of SM (d18:1/24:0) strongly upregulated several macrophage activation markers, SM (d18:1/6:0) and Cer (d18:1/24:0) however, did not. It was suggested that very long chain SM but not long chain SM were decreased in SMS2-deficient mice liver and plasma. And the exogenously added very long chain SM (d18:1/24:0) could activate macrophages directly, suggesting a novel role of plasma very long chain SM in modulating macrophage activation and resulting inflammation.

A hybrid strategy using global analysis of oxidized fatty acids and bioconversion by Bacillus circulans

RATIONALE

Targeted oxidized fatty acid analysis has been widely used to understand the roles of fatty acids in the development of diseases. However, because of the extensive structural diversity of fatty acids, it is considered that unknown lipid metabolites will remain undetected. Here, to discover and identify unknown lipid metabolites in biological samples, a global analytical system and a method of synthesizing lipid standards were investigated.

METHODS

Oxidized fatty acids in mouse lung tissues were extracted using mixed-mode spin columns. Separation was achieved via ultra-high-performance liquid chromatography, mass spectrometric (MS) analysis was conducted in full scan mode using a Q Exactive Plus instrument equipped with an electrospray ionization probe, and structure analysis was carried out by high-resolution data-dependent tandem mass spectrometry (dd-MS(2)). In addition, lipid standards, which are not commercially available, were synthesized by bioconversion using Bacillus circulans.

RESULTS

Oxidized fatty acids in mouse lung tissues were analyzed by high-resolution accurate-mass analysis, and multiple unknown molecules were discovered and tentatively identified using high-resolution dd-MS(2). Among these molecules, 21-hydroxydocosahexaenoic acid (21-HDoHE) and 22-HDoHE, which are not commercially available, were synthesized by bioconversion. By comparing the exact masses, retention times, and characteristic fragment ions of the synthesized standards, 21-HDoHE and 22-HDoHE were definitively identified in the mouse lung tissue.

CONCLUSIONS

Our strategy of global analysis and bioconversion can be used for the discovery and identification of unknown lipid molecules.