Abstract Background Despite the availability of treatment options for hepatitis D virus (HDV) management, choosing the most appropriate drug scheme for achieving virological response (VR) has not been adequately studied. Methods We conducted a systematic review and network meta-analysis of randomized trials in PubMed, EMBASE, and Web of Science databases reporting rates of VR (defined as undetectable HDV RNA or decrease by ≥ 2 log10 IU/ml at the end of treatment compared with baseline measurements). Available treatment regimens included interferon-alpha (IFN-alpha), pegylated IFN-alpha (PEG-IFN-alpha), nucleoside analogs (NA), bulevirtide (BLV), lonafarnib (LNF), combination therapy or placebo. We used random effects model and estimated odds ratio (OR) with 95% confidence interval (CI) to compare treatments based on VR. To identify the best treatment, we estimated the surface under the cumulative ranking (SUCRA) curve. Analyses were performed using the meta and netmeta packages in R (version 4.3.3). *Denotes statistically significant associations Results A total of 1322 patients from 21 studies were included in the analysis and were randomized in one of 11 treatment interventions, as described in Figure 1. Treatment duration ranged from 24 to 96 weeks. BLV + PEG-IFN-alpha was ∼6 times more likely to result in VR compared with BLV alone (OR, 5.55 [95%CI: 1.60, 19.25]). Treatment with BLV + PEG-IFN-alpha was ∼17 times more likely to result in VR compared with PEG-IFN-alpha monotherapy (OR, 16.7 [95%CI: 5.6, 49.5]) (Table 1), the main agent recommended by official guidelines for HDV management. Based on probability ranking, the most effective drug schemes for achieving VR at the end of treatment were BLV + PEG-IFN-alpha (99.7%), BLV + NA (84.4%), BLV (78%), and PEG-IFN-alpha (61.3%). Conclusion BLV + PEG-IFN-alpha is superior in achieving VR at the end of HDV treatment compared with all other available drug schemes. Further research to determine whether BLV + PEG-IFN-alpha can maintain long-term VR after end of treatment is needed. Studies should also evaluate the impact of different BLV dosages on VR. Disclosures Eleftherios Mylonakis, MD, PhD, BARDA: Grant/Research Support|Basilea: Advisor/Consultant|Chemic Labs/KODA Therapeutics: Grant/Research Support|Cidara: Grant/Research Support|Leidos Biomedical Research Inc./NCI: Grant/Research Support|NIH SciClone Pharmaceuticals: Grant/Research Support|NIH/NIAID: Grant/Research Support|NIH/NIGMS: Grant/Research Support|Pfizer: Grant/Research Support|Regeneron Pharmaceuticals, Inc.: Grant/Research Support

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), which causes coronavirus disease 2019 (COVID-19), has emerged as a global pandemic pathogen with high mortality. While treatments have been developed to reduce morbidity and mortality of COVID-19, more antivirals with broad-spectrum activities are still needed. Here, we identified lonafarnib (LNF), a Food and Drug Administration-approved inhibitor of cellular farnesyltransferase (FTase), as an effective anti-SARS-CoV-2 agent. LNF inhibited SARS-CoV-2 infection and acted synergistically with known anti-SARS antivirals. LNF was equally active against diverse SARS-CoV-2 variants. Mechanistic studies suggested that LNF targeted multiple steps of the viral life cycle. Using other structurally diverse FTase inhibitors and a LNF-resistant FTase mutant, we demonstrated a key role of FTase in the SARS-CoV-2 life cycle. To demonstrate in vivo efficacy, we infected SARS-CoV-2-susceptible humanized mice expressing human angiotensin-converting enzyme 2 (ACE2) and treated them with LNF. LNF at a clinically relevant dose suppressed the viral titer in the respiratory tract and improved pulmonary pathology and clinical parameters. Our study demonstrated that LNF, an approved oral drug with excellent human safety data, is a promising antiviral against SARS-CoV-2 that warrants further clinical assessment for treatment of COVID-19 and potentially other viral infections.

Glioblastoma multiforme (GBM) is a highly malignant brain tumor with a poor prognosis. The GBM microenvironment is highly heterogeneous and is composed of many cell types including astrocytes and endothelial cells (ECs) along with tumor cells, which are responsible for heightened resistance to standard chemotherapeutic drugs such as Temozolomide (TMZ). Here, we investigated how drug treatments impact stemness marker expression of GBM cells in multicellular tumor spheroid (MCTS) models. Co- and tri-culture MCTS constructed using U87-MG GBM cells, astrocytes, and/or ECs were cultured for 7 days. At Day 7, 5μM lonafarnib (LNF), 100 μM TMZ, or combination of 5μM LNF + 100 μM TMZ was added and the MCTS were cultured for an additional 48 h. We assessed the spheroid sizes and expression of stemness markers- NESTIN, SOX2, CD133, NANOG, and OCT4- through qRT-PCR and immunostaining. Following 48 h treatment with LNF, TMZ or their combination (LNF + TMZ), the spheroid sizes decreased compared to the untreated control. We also observed that the expression of most of the stemness markers significantly increased in the LNF + TMZ treated condition as compared to the untreated condition. These results indicate that drug treatment can influence the stemness marker expression of GBM cells in MCTS models and these aspects must be considered while evaluating therapies. In future, by incorporating other relevant cell types, we can further our understanding of their crosstalk, eventually leading to the development of new therapeutic strategies.

LBP13 - A Phase 2 Study of Peginterferon Lambda, Lonafarnib and Ritonavir for 24 Weeks: End-of-Treatment Results from the LIFT HDV Study

Lonafarnib synergizes with azoles against Aspergillus spp.and Exophiala spp.(

The prenylation inhibitor lonafarnib (LNF) is a potent antiviral agent providing a breakthrough for the treatment of hepatitis delta virus (HDV). The current study used a maximum likelihood approach to model LNF pharmacokinetic (PK) and pharmacodynamic (PD) parameters and predict the dose needed to achieve 99% efficacy using data from 12 patients chronically infected with HDV and treated with LNF 100 mg twice daily (bid) (group 1) or 200 mg bid (group 2) for 28 days. The LNF‐PK model predicted average steady‐state LNF concentrations of 860 ng/mL and 1,734 ng/mL in groups 1 and 2, respectively, with an LNF absorption rate ka = 0.43/hour and elimination rate ke = 0.045/hour. The PK/PD model identified an average delay of 0.56 hours and an LNF concentration that decreases HDV production by 50%, EC50 = 227 ng/mL, with a Hill factor h = 1.48. The HDV half‐life in blood was 1.87 days, and the average steady‐state LNF efficacy in blocking HDV production was ɛ = 87.7% for group 1 and ɛ = 95.2% for group 2. A biphasic HDV decline with an average phase 1 decline (0.9 log10 IU/mL and 1.32 log10 IU/mL) was observed in groups 1 and 2, respectively. Phase 2 was not significantly (P = 0.94) different between the two groups, with an average slope of –0.06 log IU/mL/day. The model suggests an LNF dose of ∼610 mg bid would achieve ɛ = 99%. Conclusion: The first PK/PD modeling study in patients with chronic HDV indicates that a ∼3‐fold increase in LNF dose (∼610 mg bid) would achieve 99% antiviral efficacy. A ritonavir‐boosted LNF combination may provide a means to increase LNF efficacy with minimal side effects. The modeling findings provide an important advance in understanding HDV dynamics and the basis to optimize LNF therapy for hepatitis D. (Hepatology Communications 2017;1:288–292)

FRI-115 - Pharmacokinetics and Pharmacodynamics Modeling of Lonafarnib in Patients with Chronic Hepatitis Delta Virus Infection

598 Background: LF is a potent, specific, reversible farnesyl transferase inhibitor (FTI). FT is an enzyme that catalyzes the covalent attachment of a 15-carbon farnesyl group to conserved amino acid residues at the carboxy terminus of certain proteins. FTIs were initially developed to target the ras family of oncoproteins (H-ras, K-ras, and N-ras), G-proteins that exist in a mutated (oncogenic) form in about 30% of human cancers. Oral administration of LF blocked tumor growth of a variety of human xenografts (glioblastoma, lung, pancreatic, prostate, colon, bladder, and CML) in nude mice. LF inhibits growth both ER+ and ER−, as well as HER2+ and HER2− breast cancer. We conducted a nonrandomized, open label study of LF in pts with advanced and MBC. Methods: Primary objective was to determine progression-free survival (PFS) of LF in pts with locally advanced and MBC, unlimited prior treatment, and ECOG PS 0-1. Secondary objectives included the evaluation of clinical benefit response rate (CR+PR+SD > 180 day duration), overall response rate (ORR), and toxicity. Pts 1- 4 were treated with 200mg PO BID daily on days 1-21 of every 21 day cycle until PD or unacceptable toxicity. However, due to early onset of intolerable diarrhea, the study design was modified to a dose escalation model. Pts were pre-treated with Loperamide and started on LF 200mg total daily dose (TDD). If LF was tolerated for 7 days, pts were escalated to 300mg TDD and then 400mg TDD. Results: 29 eligible pts were treated with a median of 2 cycles (range 1-7). Median age was 56 yrs (range 41-76 years), and 100% were female and ECOG PS 1. Median # of prior regimens was 8 (range 0-20). 15/24 (63%), 11/24 (46%) and 3/20 (15%) were ER, PR and HER2 positive, respectively. The most frequent grade 3/4 toxicities comprised diarrhea (23%) and dehydration (8%). Two grade 5 toxicities: PD NOS and encephalopathy. The best response data for the 17 evaluable pts are 5 (29%) stable disease (SD) and 12 (71%) progressive disease (PD). Median PFS was 9 wks. Conclusions: Results based on the first 17 pts does not support improved PFS or ORR compared to historical controls. Further follow up and biomarker correlations are ongoing and will be presented at the meeting.

Lonafarnib (LNF) is a protein farnesyl transferase (FTase) inhibitor that has shown synergistic activity with taxanes in preclinical models and early stage clinical trials. Preclinical findings suggested tubulin acetylation and FTase expression levels may be important determinants of drug sensitivity that would help identify patient populations more likely to benefit from this regimen. This pilot study evaluated the biological effects of LNF and docetaxel (DTX) combination therapy in refractory solid tumors by comparing pretreatment and post-treatment tumor biopsies. Patients with histologically confirmed locally advanced or metastatic solid malignancies refractory to standard therapies or with no effective therapies available were eligible. Patients were randomized to 1 of 4 dosing cohorts: 1) 30 mg/m², 100 mg; 2) 36 mg/m², 100 mg; 3) 30 mg/m², 150 mg; or 4) 36 mg/m², 150 mg of DTX intravenously weekly, LNF orally twice daily, respectively. Of the 38 patients enrolled, 36 were treated, and 29 were evaluable for toxicity and response assessment. The combination of LNF and DTX was tolerated in all cohorts with the exception of a 28% incidence of grade 3/4 diarrhea, which was manageable with aggressive antidiarrheal regimens. Seven patients derived clinically meaningful benefit from this combination treatment; these patients had significantly lower basal FTase-beta mRNA expression levels than the mean study population level (P < .05). Correlation of clinical benefit with tubulin acetylation content as well as basal acetyl-tubulin content were evaluated. However, no significant correlation was found. Despite the small number of patients, these findings support our preclinical mechanistic studies and warrant further clinical investigations using FTase-beta mRNA expression as a potential predictive biomarker to select for an enriched patient population to study the effects of taxane and FTase inhibitor combination therapies.

The cytoplasmic deacetylase HDAC6 is an important regulator of cellular pathways that include response to stress, protein folding, microtubule stability, and cell migration, thus representing an attractive target for cancer chemotherapy. However, little is known about its upstream regulation. Our previous work has implicated HDAC6 as a new protein target for the farnesyltransferase inhibitors (FTIs), although HDAC6 lacks a farnesylation motif. Here we show that the protein farnesyltransferase (FTase) and HDAC6 are present in a protein complex together with microtubules in vivo and in vitro. FTase binds microtubules directly via its alpha subunit, and this association requires the C terminus of tubulin. Treatment with an FTI removed FTase, but not HDAC6, from the protein complex, suggesting that the active form of FTase is bound to microtubules. Importantly, the removal of FTase from microtubules abrogated HDAC6 activity, as did a stable knockdown of the alpha subunit of FTase (FTalphaKD). Interestingly, the FTalphaKD cells showed increased sensitivity to the antiproliferative effects of Taxol and the FTI lonafarnib when used either as single agents or in combination as compared with parental cells. Altogether, these data suggest that FTase, via its tubulin-association, is a critical upstream regulator of HDAC6 activity and that FTase expression could help stratify cancer patients that would most benefit from this treatment.