Prophylactic Antiheparanase Activity by PG545 Is Antiviral In Vitro and Protects against Ross River Virus Disease in Mice

Abstract

Recently we reported on the efficacy of pentosan polysulfate (PPS), a heparan sulfate mimetic, to reduce the recruitment of inflammatory infiltrates and protect the cartilage matrix from degradation in Ross River virus (RRV)-infected PPS-treated mice. Here, we describe both prophylactic and therapeutic treatment with PG545, a low-molecular-weight heparan sulfate mimetic, for arthritogenic alphaviral infection. We first assessed antiviral activity through a 50% plaque reduction assay. Increasing concentrations of PG545 inhibited plaque formation prior to viral adsorption in viral strains RRV T48, Barmah Forest virus 2193, East/Central/South African chikungunya virus (CHIKV), and Asian CHIKV, suggesting a strong antiviral mode of action. The viral particle-compound dissociation constant was then evaluated through isothermal titration calorimetry. Furthermore, prophylactic RRV-infected PG545-treated mice had reduced viral titers in target organs corresponding to lower clinical scores of limb weakness and immune infiltrate recruitment. At peak disease, PG545-treated RRV-infected mice had lower concentrations of the matrix-degrading enzyme heparanase in conjunction with a protective effect on tissue morphology, as seen in the histopathology of skeletal muscle. Enzyme-linked immunosorbent assay quantification of cartilage oligomeric matrix protein and cross-linked C-telopeptides of type II collagen as well as knee histopathology showed increased matrix protein degradation and cartilage erosion in RRV-infected phosphate-buffered saline-treated mice compared to their PG545-treated RRV-infected counterparts. Taken together, these findings suggest that PG545 has a direct antiviral effect on arthritogenic alphaviral infection and curtails RRV-induced inflammatory disease when administered as a prophylaxis.

Synthetic Heparan Sulfate Mimetic Pixatimod (PG545) Potently Inhibits SARS-CoV-2 By Disrupting The Spike-ACE2 interaction

“…In addition to direct antiviral activity shown against SARS-CoV-2, pixatimod also has immunomodulatory effects which may alleviate some of the immunopathologies associated with moderate-severe COVID-19 patients. It inhibits the pro-inflammatory enzyme heparanase (Dredge et al, 2011) and has been demonstrated to suppress IL-6 in inflammatory (pancreatitis) and viral (Ross River virus) animal models in a process thought to be driven by elevated levels of heparanase , Supramaniam et al, 2018. Moreover, it blocks the heparanase-dependent invasion of macrophages into tumours in mouse cancer models (Ostapoff et al, 2013;Boyango et al, 2014;Barash et al, 2018).…”

“…The virucidal activity is due to disruption of the viral lipid envelope by the lipophilic steroid side chain of pixatimod (see Fig 1A), an attribute not associated with heparin or other HS mimetics (Said et al, 2016). In vivo efficacy has been confirmed in a prophylactic mouse HSV-2 genital infection model (Said et al, 2016), a prophylactic Ross River virus mouse model (Supramaniam et al, 2018) and a therapeutic Dengue virus mouse model (Modhiran et al, 2019).…”

“…Pixatimod (PG545) is a clinical-stage HS mimetic with potent anti-cancer (Dredge et al, 2011;Ferro et al, 2012), and anti-inflammatory properties Abassi et al, 2017;Koliesnik et al, 2020), but also antiviral activities (Said et al, 2010;Lundin et al, 2012;Said et al, 2016;Supramaniam et al, 2018;Modhiran et al, 2019). Significant antiviral activity for pixatimod has been reported against a number of viruses that use HS as an entry receptor with EC50's ranging from 0.06 to 14 µg/mL.…”

“…Significant antiviral activity for pixatimod has been reported against a number of viruses that use HS as an entry receptor with EC50's ranging from 0.06 to 14 µg/mL. This includes HSV-2 (Said et al, 2016), HIV (Said et al, 2010), RSV (Lundin et al, 2012), Ross River, Barmah Forest, Asian CHIK and chikungunya viruses (Supramaniam et al, 2018), and Dengue virus (Modhiran et al, 2019). In addition to blocking virus infectivity, pixatimod has also been shown to possess virucidal activity, a unique feature only found in this particular class of amphiphilic HS mimetic (Ekblad et al, 2010;Said et al, 2016).…”

Antiviral Strategies against Arthritogenic Alphaviruses

“…Pentosan polysulfate is used for the treatment of interstitial cystitis and osteoarthritis, whereas pixatimod is currently developed as an anticancer drug. Both drugs have been reported to reduce the severity of alphavirus-induced disease in vivo through the modulation of inflammatory infiltrates and cytokine levels [ 97 , 98 ]. Treatment of mice infected with RRV or CHIKV with pentosan polysulfate ( Figure 3 ) resulted in a significant disease amelioration and protection of cartilages [ 97 ].…”