Sapropterin trial, part 3: the trial

Small white pills strewn across a blank teal background.
Photo by Hal Gatewood on Unsplash

After navigating the genetics testing and establishing a baseline level, I was able to start trialling Sapropterin. I have written about these other processes in previous blogs (see links below). I had a poignant moment when I realised I was about to try my first treatment beyond restricted-diet therapy in over 40 years of living with PKU.

Sapropterin trial part 1: genetics and patience

Sapropterin trial part 2: baseline testing

The first dose of Sapropterin

The Sapropterin available on the NHS in England is a generic from a company called Teva. It is a small, white pill which is dissolved before drinking, and the dosage is worked out by a PKU clinic. The NSPKU conference in the autumn had been filled with questions about how to mask the taste. The first dosage showed me why.

Wow, that’s an intense acidity! I didn’t have the advised apple juice to dissolve the pills in. (Parents – take note and be more prepared!) I simply dissolved them in water and gritted my teeth. The dosage was quickly followed with my PKU supplement to remove the taste. How often do you do that?

I was lucky with side effects, and only had a headache the first week when starting the pills, and then at the end when coming off them. The trial took place over 4 weeks, with me taking bloods daily at first, then on alternate days. This was all done under the instruction of the clinic, and your experience may vary.

A possible response to Sapropterin

The blood spots from my first week on the pills seemed to show a drop. I admit that I began to get excited. That was a mistake, and one I’d encourage others to avoid!

The second week of the trial was awful, as I came down with a stomach bug. I did not know that I was supposed to stop sapropterin testing while I was ill. This was my third mistake. So if you are trialling Sapropterin, or any other medication, make sure you know what you are supposed to do if you become ill. And, unfortunately, the stomach bug left me quite ill.

Factors that affect Sapropterin & blood phe levels

Anecdotal reports seem to show that sapropterin is mostly negated by any illness. Further, there are three things that can lead to higher blood phe levels even when the PKU restricted diet is carefully followed: illness, sudden weight changes, and the menstrual cycle.

In the second week of the trial, while the stomach bug raged, I lost over a kilo of weight. Things started looking up towards the end of that week. However, my period then started. My blood levels for these two weeks spiked up to and over my initial baseline testing.

This was incredibly disheartening. However, in the fourth week of the trial, all my blood levels went back down below my baseline. Fortunately, my clinic agreed to apply for a second monthly trial for me. This was mainly predicated on the results of my first and final week of the trial.

A second Sapropterin trial was needed

The disruption of the bank holidays and doctors strikes the arrival of the next prescription of Sapropterin, and of the bloodspot equipment needed for trial number 2. I was able to start this in early summer, so I undertook one trial in winter and one in summer.

This second trial also held challenges beyond the already onerous tasks of recording all food, supplement, and medication intake. Three of the specially marked envelopes, which were posted into different post boxes on different days in early June, have still not turned up as I write in mid-July. This means that over a week’s worth of effort in a 4-week trial was useless. People with PKU cannot get home phe monitoring kits fast enough.

Disappointing result.

Sadly, the clinic and I did not need those missing blood results to see that I was not responding to the Sapropterin. Rather than declining, my blood spot levels were actually going up. It has been a long and challenging process, made more difficult by postal problems, strikes, illness, and plenty of emotional highs and lows. But today, I finally got the call confirming that I have completed the Sapropterin pathway as the protocols in England stand currently, and I will not be continuing on the medication.

It took 12 years for Sapropterin to be approved on the NHS, and a further 19 months for me to reach this conclusion. It is disappointing, but at least I know now! After all the effort required, it will be a relief to simply return to diet as normal – who knew I would ever feel that way! I have a new respect for all those families who are also going through this process.

Thanks to those who fought for Sapropterin

Huge thanks to the clinicians and my PKU friends who supported me, and of course to the NSPKU and those who campaigned for years for this treatment.

Next: read my tips from 6 months of nearly constant blood spots – not all lancets are equal!

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