New drug tested at USF Health Metabolic Clinic is life-changing for patient with PKU

Those helped by the new injectable enzyme therapy, recently approved by the FDA, can safely eat foods that have been forbidden for years

Patient Jennifer Mazorra, left, is examined by USF Health’s Dr. Amarilis Sanchez-Valle, a lead researcher for the clinical trial leading to recent FDA approval of the first injectable enzyme therapy for adults with the rare genetic disease PKU.

Jennifer Mazorra has spent most of her life on a diet that severely restricted what she could eat – no meat, fish, eggs, and dairy or other high-protein foods, no artificial sweeteners, and carefully measured amounts of fruits, vegetables and starches.

Mazorra, 35, was diagnosed as a newborn with the rare genetic disease phenylketonuria, or PKU, which prohibits the body from breaking down the amino acid phenylalanine found in all natural proteins. The condition is primarily controlled by a strict diet that can be difficult to maintain. If unmanaged, PKU can damage the nervous system and lead to chronic intellectual, developmental and behavioral problems.

“I was born with PKU – it’s detected by one of the screening tests that all newborns get with a heel stick. As an infant, my mother had to stop breastfeeding and give me a special formula that replaced all the essential amino acids except phenylalanine,” said Mazorra, a nurse practitioner who lives in Naples, Fla. “As a child, she was always aware that every morsel of food that went into my mouth could be tied to my IQ as an adult.”

So Mazorra enthusiastically agreed when USF Health physician Amarilis Sanchez-Valle, MD, of the USF Health Metabolic Clinic, which Mazorra visits routinely to monitor her PKU, suggested a potential option to the lifelong dietary regimen.  In 2014, Mazorra became one of the first participants in a study testing a new injectable drug for adults with PKU.

Dr. Sanchez-Valle directs the USF Health Metabolic Clinic, serving a 14-county service area in Florida, which treats children and adults with all types of hereditary errors in metabolism.

Dr. Sanchez-Valle was a lead investigator of a clinical trial for that injectable enzyme therapy, which had shown promise in breaking down and lowering blood phenylalanine concentrations in those difficult to treat with existing therapy.

The drug, Palynziq, developed by BioMarin Pharmaceutical Inc., was approved in May 2018 by the U.S. Food and Drug Administration.

It took more than a year for Mazorra to start feeling the effects of the drug, and she coped with a milder form of one of its most serious side effects, allergic reaction, by taking an antihistamine before injecting Palynziq.  (All patients treated with Palynziq must be prescribed and instructed how to use auto-injectable epinephrine in case of severe allergic reaction while taking Palynziq.) Pain, sensitivity or itching at the injection site and joint pain are the most common side effects, which typically subside quickly, Dr. Sanchez-Valle said.

The reactions were worth the effort, Mazorra said, when the therapy dropped her phenylalanine levels to normal for the first time in her life and helped her feel healthier.

“My quality of life has been so much better,” she said. “I can think more clearly now.  I’m more energetic and my mood is improved.”

Mazorra, diagnosed with PKU as an infant, has been able to attain phenylalanine levels within normal ranges by taking Palynziq.   She is part of a continuation study investigating differing doses of the new drug.

Dr. Sanchez-Valle, an associate professor of pediatrics who treats children and adults with inherited metabolic disorders from across the university’s 14-county service area, said patients traveled from as far away as Miami over the last few years seeking out a study offering a potential alternative to the PKU diet.

“It’s an exciting time for patients with PKU,” she said. “With this newly approved medication, we’re seeing what we never have before – patients eating normal diets and maintaining levels of phenylalanine within normal ranges.”

Mazorra credits Dr. Sanchez-Valle and her USF Health team for giving her the confidence to become pregnant when others had warned her of the risk of complications from maternal PKU. Babies do not inherit the disorder unless both parents carry the PKU gene, but high levels of phenylalanine in the mother can pass through the placenta as toxins, putting a child at risk for heart problems, cognitive delays and other birth defects.

Mazorra had to stop taking Palynziq weeks before and all during pregnancy, and stick to the strict diet again while battling food cravings.  It wasn’t easy, but with careful monitoring and the help of a metabolic dietitian, she and her husband are now the proud parents of a healthy 8-month-old boy, Sebastian.

Mazorra at home with 8-month-old son Sebastian and husband Gabe. | Photo courtesy of Jennifer Mazorra

Six weeks after giving birth Mazorra resumed Palynziq.  And, she is participating in a continuation study investigating differing doses of the new drug in an expanded population of adult patients to track long-term safety and effectiveness.  Dr. Sanchez-Valle is hopeful that eventually the drug will be studied in teens.

Meanwhile, Mazorra focuses more on her improved quality of life than on long-term effects. Things as simple as enjoying peanut butter toast, a snack off limits to her since childhood.

“I eat peanut butter toast every day now,” she said.

-Photos by Freddie Coleman, USF Health Communications and Marketing