PEG and PEGylation: A Historical Review of Their Evolution

[00:00:01]okay let's see how this works yeah there it is so there's my thank you and um I was going to read it it's a little hard from this angle but I can see it I want to thank active biom materialia um oh there's the thank you and for the generous very generous gold medal award it comes with $10,000 that's very generous very special and uh the society for materials I want to thank them art Cy for his gracious and superb leadership many colleagues over the years especially buddy Ratner and Pat ston who is unfortunately unable to make it here today because of the storms on the east coast and the lack of crew of airplane crews out here on the West Coast an interesting problem that I hadn't run into before and I want to thank many excellent students over over many years and especially one named Wayne gitz who's not here but he's the one who put me together with Milton Harris and led me to work more and more on Peg and um I also uh want to thank my loving family for their constant strong and lo loving support and I have a bunch of family here too so I've had breakfast with them so I want to say uh again thank you for coming and uh let's go on there's a picture of uh Kim engineering news from 2014 and it's a cartoon replication of what we imagine to be a generic nanom medicine essent essentially a pegal polymeric myell and what you're looking at is actually it's a pegal myell it it's not a polymeric myell per se because it's made up of lipid bilayer which is not polymeric but basically what you're looking at is a size scale that we're dealing with is very small hundreds of nanometers at most and um then we're dealing also with this Fuzzy Beard around the outside called Peg and that's the molecule one of the most common molecules in the field of drug delivery and biomaterials and normally when I'm at a meeting I will flip to the back and I like to look through the index of paper titles to see you know what is the focus in this meeting they don't have it in this particular program but I looked uh it's not there but I'm always finding Peg as one of the most common topics at a meeting it is the most commonly used polymer in the field of biomaterials and Drug delivery so here it is the um title of the slide says the most common molecule used in D drug delivery besides the drug of course and it's a water soluble and water binding polyether and it loves water there's um the oxygen The Ether oxygen is an electron donor and it's a very um uh happy to bond hydrogen bond to water molecules and there are estimates anywhere from two to four water molecules per uh ether oxygen so when this we'll see when this polymer increases in molecular weight and begins to form a statistically random coil um it will lock up water molecules in that coil and act like a water-filled balloon and that helps to protect drugs it also helps to whatever uh cells it may be associated with and so on so it's a very interesting protective molecule and um I would also like to say that the end group The O hydroxy there's two hydroxy per Peg molecule the end group could also be a methoxy group and that's figures in the early history of Peg the first person to discover Peg or at least look for it and find it and want to use it Frank Davis was his name um he was actually looking for MPEG methoxy Peg with an iner end so he could use the other hydroxy to attach to proteins interesting history well there are a lot of uh people in the audience I would ask for a show of hands normally but I had these U uh spotlights on me and I wouldn't see much but I will tell you that normally there are people working on pegala drugs and that is a big um and very profitable business um there are also people interested in pegula surfaces diagnostic assay people want to run a an Eliza on a surface that repels nonspecific protein binding so Peg is used for that as well and um these two communities sometimes don't interact so I want to bring them together in this talk and talk as if pegala a surface is similar in principle and also in practice to um P pagaling drugs so who where did pegal where did the idea of pegal come from it's an interesting history as I mentioned Frank Davis's uh biochemistry professor at ruter and he actually was as he said in you'll see shortly in his little article he was between grants I mean he was out of research money and looking for looking looking for ideas to uh propose to the NIH for example and get funding for his research and so um he ran into this idea of protecting the new recombinant protein drugs they were coming along in the late 60s and early 70s and that's what he wanted to do and his former student in colleague Abraham abuchowski uh was influenced by him of course and he found a company um a pegal company called enzon now I'm actually not sure why um Milton why Frank Davis wasn't more involved in that company but it may have been uh that he was he was restricted from doing it as a professor and their objective was simply to pegate to attach Peg to the new recombinant protein drugs and then to sell them as this is my characterization not theirs as new and improved types of pharmaceutical drugs so this is an article that you should all look look for two pages in the um advanced Drug delivery reviews you see it at the top there and uh right up there is the is the reference and basically I want to just quote a few P pieces of uh commentary here and this is this F very first paragraph he says he was out of research funding he was looking for a new idea and he thought about making the new protein drugs less immunogenic because they're new to the body and he thought if he attached a hydrophilic polymer of some sort that could prevent the immune system from recognizing those uh drugs those protein drugs as new and therefore needing to be eliminated from the body so they weren't seen as foreign is the point so he selected Peg as the hydrophilic polymer that he was thinking could protect them from the immune immune system recognition and um he actually was looking for not Peg he was looking for methoxy Peg so that he would have a dead end on one end and a react reactive Hydro hydroxy which he would then attach to the protein drug and uh he found it I think it was a Union Carbide chemical catalog but I'm not sure so there's a great video of Frank Davis in retirement talking about his Discovery Peg you'll enjoy it don't worry if you can't copy this down right away you just go and Google Frank Davis and um um pegal and you'll find it so this is the article that he wrote with AB Abraham Abu ch II his student who founded the company enzon a pegal the first pegal company and it was published in 1977 as you see in uh the Journal of biological chemistry and the effect of calent attachment of Peg on immunogenicity and C circulating half-life of uh the Catalyst the cataly the the model protein they first studied and and this is uh actually uh published just before Abraham abuchowski founded the company called enzyme here's a picture of it at the grand opening in 1981 and um I Le list Frank Davis there as a scientific adviser because he was not directly associated with the company as an officer I think by the way the guy in the middle there of that picture he was probably the guy with the with the bucks from The Venture cap Capital people um that's always who cuts the ribbon um so about that same time I want to bring myself into the picture here a little bit I was radiation grafting using radiation to uh chemically graft hydroxy ethylacrylate this is a monomer with one pendant ethylene glycol unit I was totally unaware of this pegal work and everybody I was working with uh and people that I was even related to in research from before like Ed Merill at MIT none of us knew about pegal from that article we never saw it so this is a mutual radiation process it's up circled up on the left and you put a polymer substrate a surface you want it to modify in a m monomer solution and then irradiate in the absence of oxygen and you get a grafted polymer on the surface it's a process called literally as you say there radiation grafting and this is the polymer that we grafted and you see the um I just point out for there are people in the audience who are like I say my relatives who are not familiar with the chemistry so this is the polymer and it goes from the left to the right and continues repeating the same um unit many many times maybe a hundred times and um it's got one ethene glycol unit so what is what we essentially produced by that grafting was a polymer that had ethylene glycose all along the backbone and it turns out it did it was very good to resist protein absorption and this is the article it's the first page of the article we published I know you can't read it but I will just uh identify the fact what we were doing there's the title of the article and the co-authors got schmear is a hematologist from the udub and uh he worked with me on that and um two students Harrison craft and U this is what was in the T table actually our Focus was on immobilizing biomolecules like heon and others and this is interesting we did never thought about the idea of making it really a new biomaterial with a hydrophilic water weding surface we we didn't really think hard about that we we knew about it but of course so grafting hydrophilic polymers on hydrophobic biomaterials surfaces and you see there two polymers that could be grafted the one on the left is what we did and the one on the right is what uh in a almost the same time period uh the toay company in Japan was were grafting that polymer on the right which has a longer tail oops sorry I forgot how to go back so anyway the the ch2 had multiple units and uh that gave it a longer and more hydrophilic uh threadlike uh like tree like with branches along the side of Peg and this is actually some of these are some of the data that they got on in terms of platelet adhesion in vitro tests and uh plasma protein absorption and what you see there is that at as the length of that side chain increases um yeah as it increases to around 50 which is a molecular weight of 2,000 roughly of a peg on the side as a side branch they essentially reached a point where they repelled all proteins and and platelets and this is an this is the first non-falling surface and it was a pegal surface so to was really the uh first company to pegate surfaces there it is and they were also the ones to highlight the importance of polymer Peg molecular weight and that's really key so this was our you know conclusion of why why it worked um surfaces with just very thin layer of uh of Peg did didn't really have the ability to resist protein absorption as you see here but as the molecular weight of the peg increased it bound the secondary water within the coil and acted like a water-filled balloon that's the imagination we don't it's not really a balloon per se but it's what we imagine how it worked and that was repelling um uh the uh proteins that are trying to push it aside and bond to the surface like you see here so it was essentially a surface that became very strongly hydrated by the Peg and with and held strongly to its water so when proteins absorb on normal surfaces they displace bound water from the surface that's an entropy gain as the water leaves the surface one molecule of protein displaces maybe 10 or 20 molecules of water so it's an entropic gain a huge Tropic gain it's not necessarily an energy phenomenon it's an entropy phenomenon phenomenon for sure so that's what I say here it was like a waterfill balloon and here's a picture of uh from the to company article in 1982 well they call it a a peo CO code you see the P oops um actually you which one yeah thank you so we're essentially looking here at a surface that got to be very clean because it repelled the bonding of proteins and platelets um it's not necessarily a biocompatible surface because it could form transient thrombi emilii that come off the surface and go down and cause some some kind of a blockage of coronary artery vessels and so on so it could the clean surface is not necessarily the best surface but it's just an example of how cleanly it was able to leave the surface so Ed Merill and Ed Saltzman also were working at that time and Ed Merill roundly publicized and talked about this uh polyethylene oxide as a uh as he says here cumulative evidence indicates a very low level of interaction between peo and biologic species cells and proteins and this polymer is essentially an important biomaterial so Ed meral is one of the um supporters and promoters of along with Ed Saltzman here of that um of the peg ability to make a non-falling surface so I need to then go and talk about pegal drugs so that's what's happening today we are pegala drugs and the drug itself might be attack uh might be a substrate for an enzyme in the body protein drug would certainly be that and so we are trying to keep those kinds of challenges away from the drug and get it to its Target site so this has become a multi-billion dollar Blockbuster pharmaceutical product and this is a table it's not I'm sorry I wish I had a better table but it it is one on you look at the T topic up uh title up there pegal products in clinical practice and here are the conjugates of Peg with with the drug and here is the medical condition that is being treated and U just underline now in in green the Blockbuster pegal drugs this is what the it says in the bottom Blockbuster is really like multi-million dollar sales and um there with asterisks you find essentially Peg interferon and Peg granulite Colony forming uh protein um and that's the other the nasta so the two are called Pegasus and neulasta and they are Blockbuster drugs I don't know I would normally in a small group ask if anybody knows somebody on one of those drugs because they are the most common drugs used to treat those particular kinds of problems leukemia and um also um hepatitis so this is a very interesting product it's multi-billion I think I had one slide but I couldn't find it said it was 11 billion dollar of sales in a few years ago 2014 so that's giving you the magnitude of what's called a Blockbuster drout and here's a little about the um conjugation of Peg to it the peg that's used is based on a uh doubly conjugated Peg on a lysine which is then attached through one of the amino groups to in in the in the pro protein which is the interferon there and it makes a an active um amid Bond rather a passive amid bond this this is a strong bond resisting hydrolysis so it's a very good way to attach to this H protein there's still a lot that's not known about pegal proteins drugs or whatever um and how much they may contribute to a an immune response but that's essentially it's been used and successfully used and with big big sales for years there's a picture however of another question you might have what if the peg goes to a million molecular weight isn't it going to block the active s of the drug and yes and this shows you work of Pascal by byan from uh uh Anon it shows you the specific activity the activity per per unit mass of Peg uh here as a function of the molecular weight of the Peg and you see as it gets bigger and bigger you essentially knock out the activity and you can imagine this Peg is getting in the way of the active side of the drug and uh so that's uh what's happening so I think they settled on a molecular weight around um between 10 and 20 somewhere in this region um it's a compromise between protection in circulation and activity as a drug so something Rec I'm getting to my last slides we have discovered not we but I mean Steve rler was one of the first that there are antibodies to Peg how can that be Peg is the most inert looking molecule it's as I say here the most innocent of polymer molecules that you could attach to a a drug and it's forming antibodies and that this is a really a kind of surprising situation and uh I think and here's an article accelerated clearance of polyethylene glycol modified proteins by anti Peg glycol IGM then this goes back to 1999 so this has been around for almost um 20 years and uh you see this is a question now of What's Happen what's going to happen to pegal drugs well people are looking more closely at it and and they are seeing that pegal drugs are actually being removed from circulation after two or three dose doses this is the Man Steve rler from uh uh from Taiwan who's made a career out of studying these antibodies both IGG and IGM antibodies to Peg well how do you avoid how do you deal with the antibodies while you try to avoid stimulating them and here are some of the people who have been working to either replace Peg or to oppose the formation of antibodies George Whitesides actually maybe 20 years ago um proposed um self assembled or Surface assembled mon molecules and layers that resisted protein absorption with zwitter ions you see those over here in this group of three of those two rather are exerion this is a group of molecules that are similarly bound to surfaces and form monol layers that are neutral but they don't have hbond donors that was another proposal of void SIDS so zeran is an interesting proposal and Professor kazuo isihara who is here today I'm glad to to see this slide uh he's been saying for years that his Witter iion which is made from a lipid mimic of of the lipid bilayer in a Cell U his his polymer which polymerizes through the bond the double bond there is a very very IM sort of innocent and inert molecule and so this is a zerion and it's also this family of polymers that are being developed to Place Peg and I put that in quotes because I don't think it's going to happen and here's another one a poly carboxy betane methacrylate so this is the backbone of the polymer up here and there's your zerion here of the cation and anion on the pendant group and here's uh some work of uh shiau Jang in our department and uh you see there these are essentially uh anti anti um IGM and IGG form formation or stimulation by um either carboxy betane gold nanop particles or pegal gold nanop particles and you can see that peg in both of these uh examples this is IGG and IGM over here Peg is really stimulating more and of these uh antibodies than PCB poly carboxy detain so Zer ions are looking very interesting as a family of molecules to essentially resist the formation of antibodies in the use of pecol drugs and that's what I see here a few slides left just to show you other compositions that are looking interesting as possible replacements for Peg and here is a good old friend Milton Harris who is a very well-known guy in the in the peg business he actually actually formed a company called sheerwater which was purchased by nectar Therapeutics and um th th that company was a very strong promoter of pegal drugs now they're looking at new compositions and I think that this is a good statement greater than $120 billion dollar of cumulative product sales can be attributed to the old-fashioned pegal drug technology that he and his partner Mike Bentley some superb chemists uh who essentially made a lot of money on that in that field so here's what he's working on now it's a poly oxazoline a water soluble very benign polymer and uh there there you see the structure uh Jean fret was at a meeting I was at in Tokyo um celebrating kataoka uh kazuk kazori kataoka's retire enironment and here's the list that he showed in his talk about two carriers that might replace Pagan and you see the first one is a hydroxypropyl meth acryloid and the other one en vinyl peridone here those are very well-known simple polymers and uh they're also very hydrophilic like Peg and very water soluble like Peg and uh and so on so let me just continue to the next slide and this is RA Heather Maynard's wheel of biocompatible uh uh polymers that could potentially replace Peg and they're in three categories biodegradable non-biodegradable and branched and comb and you'll see some of the titles there is Wier ions well it's not there it is polyoxy azeline pegma and so on so I'm going to stop here and just tell you that the future is wide open for Peg and pegal drugs and I think they're going to stay around for a long time I think if the FDA did anything to to essentially reject their use in any way it would be Earth shaking to the industry so I think pegal drugs are here to stay it's an optimistic but I think a happy conclusion even though where we see these problems coming up thank you very [Applause] much