CRV431 is a derivative of cyclosporine that has exhibited inhibitory effects of several different proteins in the cyclophilin family. A widely known cyclophilin antagonist is cyclosporin A (CsA), which reshaped solid organ transplantation after its approval in 1983 as an immunosuppressant. The immunosuppressant activity of CsA is driven by its inhibition of calcineurin, and cyclophilin binding appears secondary to this function. Cyclophilins are enzymes that facilitate proper protein folding and have been implicated in NASH, liver fibrosis, HCC, and other liver diseases making these enzymes potential therapeutic targets. Specifically, cyclophilins catalyze the cis-trans isomerization of proline peptide bonds. A high proportion of collagen is comprised of proline, an amino acid, and cyclophilins regulate a key step in the biochemical process that leads to the proper folding of proline. If proline is not folded correctly, then collagen formation could be hampered which would then also possibly affect liver fibrosis.
Three cyclophilins have been implicated in contributing to the manifestation of NASH and liver fibrosis: CypA contributes to collagen formation in liver cells, CypB modulates collagen cross-linking, and CypD plays a central role in regulating the mitochondrial pore. Theoretically, the reduction of collagen formation and cross-linking could affect the development of collagenous tissue, such as skin, tendon, and bone; however, cyclosporine has not been observed to affect such development. Additionally, Hepion has not reported adverse side-effects stemming from the downstream effects of cyclophilin inhibition in its preclinical work or human studies.
With substitutions at amino acids 1 and 3 of the cyclosporine ring, Hepion claims that CRV431 inhibits CypA, CypB, and CypD without the immunosuppressant feature characteristic of CsA. The company proposes that CRV431 has a very low affinity for binding calcineurin which should remove the immunosuppression effect. In turn, Hepion believes this would allow CRV431 to decrease liver fibrosis by affecting the causative processes in hepatic stellate cells, which are the primary collagen-producing cell types implicated in liver fibrosis. The company noted that: 1) decreased expression of fibrosis-related genes; and 2) decreased CypB-dependent collagen synthesis and secretion are a result of CRV431 action.
While CsA was shown to exhibit clinical toxicities, such as nephrotoxicity, hypertension, and dyslipidemia, it is suggested these side effects appeared to be a function of the immunosuppressive activity rather than cyclophilin binding. The company believes CRV431 is unlikely to cause these clinical toxicities, specifically nephrotoxicity, since the proposed mechanism of action excludes calcineurin binding. Additionally, Hepion cited alisporivir, a non-immunosuppressive CsA analog, was dosed to over 2,000 patients at high doses with no renal toxicity. The company reported that preclinical toxicology studies of CRV431 implied a good safety profile and is currently conducting a multiple ascending dose Phase I study.
Hepion holds a composition of matter patent (US 9,200,038) on CRV431. This patent extends through to 2030 and could gain an additional five years under the Hatch-Waxman Act. In 2017, the company was granted a new patent (US 9,714,271) which ends in 2031. Hepion cited the new patent significantly extends the claims of the original CRV431 patent family allowing for a broad coverage of many compounds within their library of cyclophilin inhibitors
Selected preclinical history
Hepion was initially developing CRV431 for the treatment of hepatitis B; however, the company shifted its focus to NASH in 2019 as Hepion felt the preclinical data for NASH was more compelling than for hepatitis B. Hepion has reported results from several preclinical animal models with chemically induced NASH and/or liver injury with liver fibrosis (Exhibit 4). Data across those studies (mostly conducted by third parties and partially funded by the company) have consistently shown results suggesting CRV431’s potent anti-fibrotic effects alongside a comparator drug panel of other NASH-drug candidates currently in development, as explained below.
Exhibit 4: Summary of non-clinical anti-fibrotic activities
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Source: Hepion Pharmaceuticals
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In November 2019, Hepion published CRV431 results in mouse models of liver fibrosis and NASH.21 Liver fibrosis in mice was induced via chronic dosing of carbon tetrachloride (CCl4), a hepatotoxin known to cause liver injury, at which point 50mg/kg/day of CRV431 was orally administered for six weeks. As a comparator, Ocaliva, which is also in development as a NASH treatment by Intercept Pharmaceuticals (and already FDA-approved for primary biliary cholangitis), was included and dosed at 10mg/kg/day. Results showed that CRV431 decreased the amount of fibrosis by 43% when compared to Ocaliva (at 10mg/kg/day), which showed no significant effect. Also, in mice treated with a combination of CRV431 and Ocaliva, fibrosis reduction was similar to that of CRV431 alone. Of note, Intercept cited that Ocaliva dosed at 25mg/day in humans significantly improved fibrosis and key components of NASH versus a 10mg/day dose.
In a second mouse model, streptozotocin followed by a high fat diet was used to induce diabetes and a fatty liver. Oral daily treatment with CRV431 at 50mg/kg showed decreased fibrosis levels of 37% to 46%, when compared to the control group, at treatment durations of 3-14 weeks, 8-14 weeks, and 20-30 weeks (Exhibit 5).
Exhibit 5: NASH mouse model preclinical data
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Source: Hepion Pharmaceuticals
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Similar results were seen in different study of rats were treated with thioacetamide to induce liver injury and fibrosis either in combination with CRV431 or vehicle control. Hepion reported that of the 10 rats treated with CRV431, none displayed development of cirrhosis, while five of 10 rats in the control group did develop cirrhosis. Using a histological stain to measure fibrotic scarring, a mean reduction of 49% in the CRV431-treated group was shown when compared to the control group, which the company claimed to suggest that CRV431 was primarily responsible for attenuating the progression of cirrhosis during the study.
In November 2019 and January 2020, the company reported results from two studies utilizing human precision cut liver slices (PCLS) where the tissue was exposed to transforming growth factor beta (TGF) and platelet-derived growth factor (PDGF) to induce of inflammation and fibrosis.
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In the first study, Hepion cited that CRV431 was found to be 100% effective in preventing fibrosis induction beyond baseline levels when administered concurrently with TGF and PDGF. The company stated that CRV431 was also shown to be more effective at preventing fibrosis than Genfit’s elafibranor and Intercept’s Ocaliva with each comparator exhibiting 62% and 9% effectiveness in decreasing fibrotic activity, respectively.
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The second study expanded on the first utilizing three donor PCLS and included the addition of Madrigal Pharmaceutical’s resmetirom and Galmed Pharmaceutical’s aramchol to the comparator drug panel. The company cited that the comparator compounds were administered at equal or higher doses than CRV431, but no specific values were discussed or provided. For reference, dosages in recent clinical trials of resmetirom and aramchol have been reported at 100mg and 600mg per day. This implies that while an efficacious dose level of CRV431 could have been utilized, it is unclear whether the tested concentrations of resmetirom or aramchol would demonstrate meaningful therapeutic effects. Hepion noted that CRV431 demonstrated prevention of experimentally induced liver fibrosis more than the other NASH drug candidates assessed and exhibited decreased gene expression and secretion of several markers of inflammation and fibrosis, including interleukin-6 (IL-6), monocyte chemoattractant protein-1 (MCP-1), collagen type I α1, hyaluronic acid, and tissue inhibitors of matrix metalloproteinases-1 (TIMP-1). The company cited a combined data analysis of the two studies showed that, on average, CRV431 was the only drug candidate to completely prevent TGF- and PDGF-induced fibrosis.
In assessing future potential applications of CRV431 following NASH as the initial indication, Hepion announced results from studies that suggest CRV431 decreased production of extracellular matrix (ECM) molecules, such as collagen and fibronectin, in fibroblast cells derived from several different organs. The cell types utilized in the study were lung fibroblasts from a patient with idiopathic pulmonary fibrosis (IPF), cardiac fibroblasts, dermal fibroblasts, renal mesangial cells, and LX2 hepatic stellate cell line. The collagen and fibronectin over-production in these cell types have been implicated in fibrotic scarring of injured organs. The company stated that CRV431 dose-dependently decreased procollagen and fibronectin secretion in all cell types with similar magnitude. Hepion believes CRV431’s inhibition of cyclophilin B reduced ECM molecule production leads to the possibility that CRV431 could be evaluated for a host of other disorders.
Since CypB is expressed in all cell types, its downstream inhibition could have adverse effects on collagenous tissue. One study conducted in mouse models of osteogenesis imperfecta (OI), brittle bone disease, suggested that deletion of CypB resulted in abnormal bone development in newborn mice and osteoporotic features in adult mice. CRV431 is known to down-regulate CypB, but gene deletion (knockout) is often expected to show more severe phenotypic effects than protein down-regulation using a drug, in part because gene deletion eliminates the protein during animal growth and development. Moreover, Hepion’s chief scientific officer, Dr Daren R. Ure, and colleagues noted that even though the genetic deletion of CypB results in severe effects on collagenous tissue development, pharmacologic inhibition (such as through CRV431) has not shown such significant tissue disturbances.
While still focusing on hepatitis B, Hepion completed a Phase I single ascending dose (SAD) study October 2018 to evaluate the safety and tolerability of single doses of CRV431 at increasing dosages, while also assessing the pharmacokinetics (PK). A total of 32 healthy subjects were enrolled and dosages of 75mg, 225mg, 375mg, and 525mg were administered. The company reported a favorable safety profile and no serious adverse effects (SAEs) occurred and noted only mild to moderate adverse effects (AEs) mostly unrelated to the study. The types of AEs reported included gastrointestinal and (non-specified) nervous system disorders, among others. None of the AEs were grade 3 or 4 and rates were similar to that of the placebo group. Following the completion of the SAD study, Hepion shifted its focus to NASH and initiated the Phase I multiple ascending dose (MAD) study in August 2019 to evaluate the safety and tolerability of multiple oral doses of CRV431. Utilizing 16 healthy volunteers, study doses were set at 75mg, 150mg, 225mg, and 300mg and administered over 28 days. The company reported that the 75mg, 150mg, and 225mg levels were safe and well tolerated, which allowed commencement of the 300mg dosage level in May 2020. Hepion cited that higher doses may need to be explored to fully assess CRV341’s safety and maximum tolerated dose, but that will be determined following completion of the 300mg cohort.
Hepion intends to initiate a Phase IIa pilot trial, dubbed AMBITION, in June 2020 with expected results by year end. The main objective of the study is to assess the safety and tolerability of a once daily 75mg dose of CRV431 over 28 days. The secondary objective is to assess anti-fibrotic activity of CRV431 and to generate exploratory anti-fibrotic biomarker data, such as collagen biomarkers, matrix metalloproteinases, lipidomics, and genomics. The study will be a multi-center, single-blind, placebo-controlled design with a cohort of 18 subjects who have presumed NASH with stage 2 or 3 fibrosis. Twelve subjects will receive the drug and six will receive placebo. The company also plans to initiate another Phase II NASH study in H121 with approximately 100 patients to assess the efficacy of CRV431 over the course of 24 weeks.
Competition: A crowded space
There are currently no approved medications for NAFLD or NASH in the US, but given the high prevalence of NAFLD and NASH, there has been significant effort to develop drugs for these large markets with an FDA decision on Ocaliva is expected in coming weeks. Hence, there is a reasonable probability that at least one NASH therapeutic will be approved and on the market by the time CRV431 completes clinical development.
There are currently over 200 ongoing clinical studies for NAFLD and NASH on clinicaltrials.gov representing the scope of activity seen in this space. Moreover, there have been a large number of deals in the space. Gilead alone signed three NASH deals in 2019: with Insitro (preclinical, $15m upfront, $235m milestones, low double digit royalties), Glympse Bio (biomarker collaboration, terms undisclosed), and Novo Nordisk (combination therapy partnership, terms undisclosed). Other prominent recent deals include Boehringer Ingelheim’s preclinical deal with Yuhan ($40m upfront, $830m milestones, tiered royalties), and Novartis’s preclinical deal with Pliant ($80m upfront, undisclosed milestones, tiered royalties).
Clinical trial timelines were significantly shortened once the FDA adjusted its guidelines so that new drug candidates only need to show a reduction of severity of liver inflammation (steatohepatitis) and fibrosis as primary endpoints, compared to the previous standard of having to demonstrate that fewer patients progressed to cirrhosis or died of liver failure. The former standards could take several decades to observe outcomes, while the updated guidelines are much shorter with tissue changes that can be measured over 6–24 months. NASH therapeutics currently in development fall under several different drug classes (Exhibit 6), which can generally be grouped into two categories: those that aim to treat liver disease directly by addressing fibrosis (such as CRV431) or inflammation, and those that aim to treat the underlying causes, such as glucose metabolism or hyperlipidaemia. Drugs that inhibit apoptosis signal-regulating kinase 1 (ASK1) and C-C motif chemokine receptors 2/5 (CCR2/5) target liver disease directly, while farnesoid X nuclear receptor (FXR), peroxisome proliferator activated receptors alpha/delta (PPARα/δ), and thyroid hormone receptor beta (THR-β) agonists treat the underlying causes.
Exhibit 6: Selected companies with NASH drug candidates in Phase III trials
Company & compound |
MOA |
Clinical Trial Phase |
Timelines |
Intercept Pharmaceuticals; Obeticholic acid (OCA) |
FXR |
Phase III (REGENERATE) |
NDA submitted in September 2019; market approval potentially in H220 |
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Phase III (REVERSE) |
Estimated study completion by June 2021 |
Madrigal Pharmaceuticals; Resmetirom |
THR-β |
Phase III |
Interim analysis results expected H121 |
Allergan; Cenicriviroc (CVC) |
CCR2/5 |
Phase III |
Currently enrolling patients; estimated study completion in H220 |
Source: Edison Investment Research
Intercept Pharmaceuticals filed a New Drug Application (NDA) to the US Food and Drug Administration (FDA) in September 2019 for its synthetically modified bile acid Ocaliva in the treatment of fibrosis and in May 2020 it announced that the 9 June 2020 FDA advisory committee meeting relating to the NDA has been postponed to accommodate the review of additional data requested by the FDA, which we anticipate would push back a potential NDA decision into H220. Ocaliva (obeticholic acid, OCA) is an FXR agonist and in 2019, Intercept reported interim Phase III clinical trial results from its REGENERATE study for OCA and one of two primary endpoints were met. The first primary endpoint, improvement in fibrosis, was met with data showing OCA led to an improvement of one stage or greater in fibrosis without worsening of NASH after 18 months. Of the second primary endpoint, resolution of NASH, OCA did not lead to significantly more frequent resolution of NASH without the worsening of fibrosis. Of note, 51% of patients taking OCA reported experiencing mild to moderate itching as a side effect and 9% of those individuals stopped take the drug as a result. Meanwhile, the company completed enrolment in January 2020 for its other Phase III study, REVERSE, which aims to evaluate OCA in the treatment of compensated cirrhosis due to NASH.
Madrigal Pharmaceuticals is solely focused on the treatment of NASH and initiated two Phase III studies in March 2019. The company’s lead asset, MGL-3196 (resmetirom), is a thyroid hormone receptor beta (THR-β) selective agonist and the first Phase III study, MAESTRO-NASH, will assess resmetirom’s efficacy in the treatment of NASH in patients with stage 2-3 fibrosis, while the second Phase III, MAESTO-NAFLD-1, is a safety and biomarker study. Madrigal expects interim data results in H121 following the second liver biopsy in patients after 52 weeks of treatment and the company stated it plans to file for accelerated approval based on those results. In a Phase II study completed in February 2018, 25% of all patients treated with resmetirom and 37% of patients treated who were on adequate doses of the drug met the Phase III NASH resolution endpoint.
Allergan entered the NASH space by acquiring Tobira Therapeutics in 2016 after the lead drug, cenicriviroc (CVC), a CCR2/5 antagonist that had failed a Phase IIb trial when it missed the primary endpoint of reducing a NASH activity score (NAS) score by two points. However, CVC did meet one secondary endpoint of improving fibrosis by at least one stage without worsening of NASH. Allergan is running the Phase III trial now with an expected top-line readout in Q420. In April 2017, Allergan initiated a Phase IIb study to test CVC’s efficacy as a combination with Novartis’ FXR agonist, tropifexor. The study is still enrolling approximately 200 patients and the estimated trial completion date is H220.
Previously at the Phase III stage was Genfit’s elafibranor, a dual PPAR α/δagonist, which was recently reported to have failed to meet the primary endpoint (of NASH resolution without worsening of fibrosis). Elafibranor previously also missed the primary endpoint in a Phase II NASH study in 2015 as Genfit cited that inclusion of too many patients presenting with early-stage NASH led to the study’s failure; however, the company proceeded to design the Phase III trial by focusing on patients with more severe NASH progression. Genfit was also expected to initiate a proof-of-concept combination drug study in Q120, but had delayed it due to COVID-19. In light of the recent Phase III failure, the future of this study is unknown. The study was expected to evaluate elafibranor efficacy in combination with other diabetes drugs, such as sodium-glucose transport protein (SGLT2) inhibitor or glucagon-like peptide 1 (GLP-1) receptor agonist.