What the heck is PEG-PAL??

Hey all! I’ve been seeing lots of posts on my PKU groups on Facebook asking about PEG-PAL, so I decided to write a post about my experiences with this PKU wonder-drug. If ever there was a time to have PKU….IT’S NOW. This drug is a REVOLUTION! Here we go:

The Drug

PEG-PAL is, in a nut-shell, an injectable enzyme that replaces the one that’s deficient in people with PKU. Though it’s not the exact same enzyme we’re missing, it’s similar. PKU people are lacking phenylalanine hydroxylase, an enzyme that converts phenylalanine to tyrosine. Without this enzyme, phenylalanine we acquire from our diet is not broken down by the body, and builds up in our bloodstream and brain, causing brain damage. Also, since phe isn’t converted to tyrosine by PKU people, tyrosine becomes an “essential” amino acid in us, meaning tyrosine is something we have to acquire via our diet since it is not made by our bodies. PEG-PAL on the other hand is a phenylalanine ammonia lyase. Fancy words saying it breaks down phenylalanine, but to different harmless components (not tyrosine). The PEG in PEG-PAL stands for pegylated. Pegylating something means coating it in a substance called Poly Ethylene Glycol (PEG), which basically masks the substance from the host’s immune system, preventing an immune/allergic response, and helping the substance last longer. For those of you who are familiar with the Depo-Provera birth control shot you can get every three months, it is also pegylated.

Background

I’m 25 and currently live in Omaha, Nebraska where the only PKU (metabolic) clinic in the state is located. Even more convenient, I’m a third year medical student at the University of Nebraska Medical Center. I’ll be a doctor in a year, yay! So it’s fair to say I’m at the hospital fairly frequently. I tried Kuvan, another FDA-approved Biomarin drug for PKU, and unfortunately didn’t respond. Since then, I’ve been bugging my doc about this PEG-PAL thing and involving Nebraska in one of Biomarin’s (the PEG-PAL creators) clinical trials. Hallelujah they listened! Last winter I was notified UNMC’s proposal to become a study site for the PEG-PAL trials. Side note… props to my physician for making this happen. There’s an unbelievably complex time-consuming, tree-killing, paper-dense process sites must go through to become “approved” for such a study. The man-power and time it takes to make this happen is crazy…but that’s a whole separate story.

Initial Trial

I was recruited to be one of two initial study participants at the Nebraska site. The first “visit” consisted of signing about 20 pages of consent forms basically stating what the trial was about, the risks involved, and if I consented to things like blood sample donation and skin biopsies if I had a reaction to the drug.

Next, I went through a battery of tests. Probably 10 tubes of blood were drawn initially to check base phe levels, kidney function, electrolytes, etc. If you’re not a fan of blood draws, like I was, you’ll quickly get used to them while in this trial. I also had a physical exam done, chest X-ray, and EKG to look at my heart function. All were normal, so I started the trial.

The first few months consisted of me coming in to clinic and receiving a low-dose injection of PEGPAL given to me in the fat layer of my arm by a nurse. Then I sat….for 30 boring minutes…to monitor for any reactions I might have to the drug. They slowly increased the dose of PEG-PAL I was receiving over the weeks, and the frequency I’d get the injections. I finally found a dose that kept my phe levels in a “goal-range” (less than 6 I think).  By that time, I was trained to give myself the injections and was allowed to take the drug home, where I’d give myself the shot once a day, five days per week. I also kept strict diet journals to turn in before my weekly blood draws.

Since then, I’ve been through a few more subcategories of the trial where my injection schedules or doses have changed, each time having to go through the million blood tubes (or so it seems), physical, X-ray, and EKG. I’ve slowly liberalized my diet over the last year and now it’s largely a “normal person diet!” I’m including starches, dairy (cheese, milk, yogurt), and MEAT (chicken, beef, seafood, etc) and my phe levels continue to be UNDETECTABLE! I feel the best I’ve felt since my mom was controlling everything that went in my mouth at age 2.

Injections!

Here’s some pics of tonight’s injection so you can see how the process works. Although a daily shot with – shudder – needle may sound a bit scary, it’s a small price to pay for perfect phe levels! The shot itself barely hurts. It goes into the subcutaneous (fat) layer just below your skin, and uses a small, short 25 gauge needle. Easy as pie after a couple practice sessions!

Here’s PEGPAL in it’s individual vials. The small black-and-white screen is called a TagAlert and indicates if the environment of the drug (AKA my fridge) is the appropriate temperature. I have to check it before drawing up the drug.

My PEGPAL log book where I keep track of where and when I give my injections, my tyrosine supplements, and any reactions I’ve had.

In my current sub-study, I’m supposed to take three 500 mg capsules of tyrosine per day. I keep track of my tyrosine in the booklet.

The supplies I use every night I do an injection. 2 alcohol swabs (for cleaning off vials and my skin), one cotton ball (for any small amount blood or drug that leaks out after injection), a 3 mL syringe with big needle (to draw up drug), a small needle (to inject drug), and 2 vials of PEGPAL.

I first draw up the drug from the vials into the syringe. My current dose is 2.67 mLs.

Once drug is drawn up, I switch the syringe to the SMALL needle, then clean off my injection site with an alcohol swab. You can inject PEGPAL into your abdomen, thighs, or upper arms…pretty much anywhere with a fatty layer. I have no problem finding one of these areas. 🙂

Poke and sometimes a burn! It’s kind of hit and miss regarding if the injection hurts or not. Some spots of my abdomen are more sensitive than others to the poke of the needle. Usually it’s painless!

Voila! I massage the injection site for a second to help the drug absorb, cover it with a cotton ball for a minute or two, and am done till tomorrow!

 

Side Effects

I’ve been very fortunate when it comes to side effects for PEG-PAL. I initially  had none, then began getting occasional hives on both of my upper arms. The were itchy and warm to the touch, but subsided after an hour. I now take a Claritin or Allegra (non-drowsy antihistamine) everyday to prevent the hives and have no problems with them! This is the most common side effect and usually subsides after a few months on its own or with an anti-histamine.  Other things I noticed: the lymph nodes in my groin area seemed a bit swollen after I started the injections. Makes sense. You’re injecting a protein with a protective coating your body isn’t used to seeing, so my lymph nodes (part of immune system) got a bit bigger after introducing PEGPAL. I also get headaches occasionally, but so does everyone else right? Who knows if this is related to PEG-PAL or if it’s just me.

The other more serious side effects I’ve heard of other trial members having are worse, more extensive rashes than mine, rigors (or shakes), and one person with syncope (fainting spells). These are RARE and you’re monitored closely throughout the trial with blood tests and checkups to make sure your body is tolerating the drug well.  You’re also given an Epi-Pen should you have a serious allergic reaction call anaphylaxis, which can affect your airway. I haven’t heard of any PEGPAL users having an anaphylactic reaction.

From what I’ve read, it sounds like you can predict how you’ll react to PEG-PAL by looking at how your immune system acts normally. People who have an overactive immune system, or who are “atopic,” are more likely to have more reactions than those with less active immune systems. An atopic person is usually someone with severe allergies (seasonal, food, etc.), eczema, and/or asthma. I myself am fairly atopic as I have some pretty significant seasonal allergies. Despite my happy-go-lucky immune system, my side effects are virtually non-existent with my daily anti-histamine.

The End

I guess my goal for this post was just informing anyone who wants to know more about PEG-PAL what it is and how it works. Hope this was helpful! Please feel free to contact me via comments on this post or on Facebook with any comments or questions you have! I love to hear from people, especially about anything PKU!  🙂

-Jenn