Development of Improved Synthetic Routes to Pixatimod (PG545), a Sulfated Oligosaccharide-Steroid Conjugate

Chhabra, Mohit; Wimmer, Norbert; He, Qi Qi; Ferro, Vito

doi:10.1021/acs.bioconjchem.1c00453

Cited by 8 publications

(14 citation statements)

References 33 publications

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“…The signal for H1 appears as a doublet with J 1,2 =4.97 Hz which is similar to that reported for fully sulfated methyl β‐D‐glucoside ( J 1,2 =5.0 Hz) [14d] which displays a skew boat‐like conformation intermediate between 3,O B and 3 S 1 . In comparison, the corresponding doublet for non‐sulfated PG545 ( 2 ) [15] shows J 1,2 =7.77 Hz (Figure 3A) which is in the typical range for a 4 C 1 chair conformation. Furthermore, strong H5−H1 and negligible H5−H3 NOEs (Figure 3B) confirm a distorted ring conformation (the H5−H3 NOE should be strong if the sugar was in a conventional 4 C 1 conformation).…”

Section: Resultsmentioning

confidence: 92%

Structural Insights into Pixatimod (PG545) Inhibition of Heparanase, a Key Enzyme in Cancer and Viral Infections

Chhabra

Wilson

et al. 2022

Chemistry A European J

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Pixatimod (PG545), a heparan sulfate (HS) mimetic and anticancer agent currently in clinical trials, is a potent inhibitor of heparanase. Heparanase is an endo‐β‐glucuronidase that degrades HS in the extracellular matrix and basement membranes and is implicated in numerous pathological processes such as cancer and viral infections, including SARS−CoV‐2. To understand how PG545 interacts with heparanase, we firstly carried out a conformational analysis through a combination of NMR experiments and molecular modelling which showed that the reducing end β‐D‐glucose residue of PG545 adopts a distorted conformation. This was followed by docking and molecular dynamics simulations to study the interactions of PG545 with heparanase, revealing that PG545 is able to block the active site by binding in different conformations, with the cholestanol side‐chain making important hydrophobic interactions. While PG545 blocks its natural substrate HS from binding to the active site, small synthetic heparanase substrates are only partially excluded, and thus pentasaccharide or larger substrates are preferred for assaying this class of inhibitor. This study provides new insights for the design of next‐generation heparanase inhibitors and substrates.

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Section: Resultsmentioning

confidence: 92%

Structural Insights into Pixatimod (PG545) Inhibition of Heparanase, a Key Enzyme in Cancer and Viral Infections

Chhabra

Wilson

et al. 2022

Chemistry A European J

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“…Samples were then centrifuged at 2000 g for 10 min at 4°C and plasma was aliquoted and stored at −80°C for downstream analysis. Certain samples were pretreated with the following for 30 min at 37°C: SFMI‐1 (MASP1/2 inhibitor 10 μ m ; synthesised in house 27 ), LNP023 (factor B inhibitor, 10 μ m ; AdooQ Bioscience, Irvine, CA, USA; #A18905), compstatin analogue (C3 inhibitor, 20 μ m ; Wuxi AppTec Ltd, Shanghai, China; #C15031904), eculizumab (C5 inhibitor, 100 μg mL −1 ; Ichorbio, Wantage, UK; #ICH4005), EGCG (heparan sulfate inhibitor, 100 μ m ; Sigma‐Aldrich; E4143‐50MG) or pixatimod/PG545 (heparan sulfate mimetic, 100 μg mL −1 ; synthesised in house 28 ). This assay was repeated with plasma isolated from whole blood after centrifugation at 2000 g for 10 min at room temperature.…”

Section: Methodsmentioning

confidence: 99%

SARS‐CoV‐2 triggers complement activation through interactions with heparan sulfate

Amarilla

Lee

et al. 2022

Clin & Trans Imm

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Objectives To determine whether SARS‐CoV‐2 can trigger complement activation, the pathways that are involved and the functional significance of the resultant effect. Methods SARS‐CoV‐2 was inoculated into a human lepirudin‐anticoagulated whole blood model, which contains a full repertoire of complement factors and leukocytes that express complement receptors. Complement activation was determined by measuring C5a production with an ELISA, and pretreatment with specific inhibitors was used to identify the pathways involved. The functional significance of this was then assessed by measuring markers of C5a signalling including leukocyte C5aR1 internalisation and CD11b upregulation with flow cytometry. Results SARS‐CoV‐2 inoculation in this whole blood model caused progressive C5a production over 24 h, which was significantly reduced by inhibitors for factor B, C3, C5 and heparan sulfate. However, this phenomenon could not be replicated in cell‐free plasma, highlighting the requirement for cell surface interactions with heparan sulfate. Functional analysis of this phenomenon revealed that C5aR1 signalling and CD11b upregulation in granulocytes and monocytes was delayed and only occurred after 24 h. Conclusion SARS‐CoV‐2 is a noncanonical alternative pathway activator that progressively triggers complement activation through interactions with heparan sulfate.

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“…Such mixtures present a significant barrier for regulatory approval. Interestingly, pixatimod, a homogeneous sulfated tetrasaccharide, carries a cholestanol moiety at the reducing end. , Yet, as with most oligosaccharides, the total synthesis of pixatimod has been reported to be challenging …”

Section: Discussionmentioning

confidence: 99%

“…37,38 Yet, as with most oligosaccharides, the total synthesis of pixatimod has been reported to be challenging. 40 Overcoming the barrier of oral bioavailability will enhance the applicability of GAGs and GAG mimetics as drugs. None of the above GAG-based molecules, including pixatimod, 38 in clinical trials are being administered orally.…”

Section: ■ Discussionmentioning

confidence: 99%

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Designing Synthetic, Sulfated Glycosaminoglycan Mimetics That Are Orally Bioavailable and Exhibiting In Vivo Anticancer Activity

et al. 2023

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Sulfated glycosaminoglycans (GAGs), or synthetic mimetics thereof, are not favorably viewed as orally bioavailable drugs owing to their high number of anionic sulfate groups. Devising an approach for oral delivery of such highly sulfated molecules would be very useful. This work presents the concept that conjugating cholesterol to synthetic sulfated GAG mimetics enables oral delivery. A focused library of sulfated GAG mimetics was synthesized and found to inhibit the growth of a colorectal cancer cell line under spheroid conditions with a wide range of potencies ( 0.8 to 46 μM). Specific analogues containing cholesterol, either alone or in combination with clinical utilized drugs, exhibited pronounced in vivo anticancer potential with intraperitoneal as well as oral administration, as assessed by ex vivo tertiary and quaternary spheroid growth, cancer stem cell (CSC) markers, and/or self-renewal factors. Overall, cholesterol derivatization of highly sulfated GAG mimetics affords an excellent approach for engineering oral activity.

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Development of Improved Synthetic Routes to Pixatimod (PG545), a Sulfated Oligosaccharide-Steroid Conjugate

Cited by 8 publications

References 33 publications

Structural Insights into Pixatimod (PG545) Inhibition of Heparanase, a Key Enzyme in Cancer and Viral Infections

Structural Insights into Pixatimod (PG545) Inhibition of Heparanase, a Key Enzyme in Cancer and Viral Infections

SARS‐CoV‐2 triggers complement activation through interactions with heparan sulfate

Designing Synthetic, Sulfated Glycosaminoglycan Mimetics That Are Orally Bioavailable and Exhibiting In Vivo Anticancer Activity

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