Jnana Therapeutics Announces Positive Clinical Proof of Concept Achieved With Potential First-in-Class Oral Treatment for PKU

Jnana Therapeutics recently announced positive, statistically significant interim results from its ongoing clinical study of JNT-517 in individuals with phenylketonuria (PKU). JNT-517, a small molecule inhibitor of the phenylalanine (Phe) transporter SLC6A19, is being evaluated as a potential first-in-class oral treatment for PKU across all ages and genotypes. On the basis of these positive interim results, Jnana has adapted the Phase 1b trial design to support the potential for accelerated progression of JNT-517.

“There is an urgent need for an oral, safe, and efficacious therapy for the more than 60% of individuals with PKU not currently on therapy. Across the spectrum of mild to severe disease, our results demonstrate a robust, sustained reduction in blood Phe levels, the registrational endpoint for PKU, giving us high confidence in the path forward for JNT-517,” said George Vratsanos, MD, Chief Medical Officer and Head of R&D at Jnana Therapeutics. “We are also encouraged by this validation of the power of our RAPID platform to discover small molecules with compelling clinical benefit against challenging-to-drug targets.”

JNT-517 is being studied in a randomized, double-blind, placebo-controlled trial in individuals with mild to severe PKU. Following a 28-day screening period focused predominantly on ensuring an average blood Phe level of >600µM, study participants were randomized with no run-in period to 75mg of JNT-517 twice daily (BID) or placebo.

The planned interim analysis was based on 13 participants, eight dosed with JNT-517 and five dosed with placebo over 28 days, and demonstrated the following results:

• JNT-517 led to a statistically significant (p=0.0019 vs. placebo) mean blood Phe reduction from baseline of 51%, measured per-protocol at day 28.
• A high response rate was seen where seven of eight (88%) treated participants achieved >30% reduction in blood Phe from baseline; five of eight (63%) achieved >45% reduction; and two of eight (25%) achieved >65% reduction.
• A robust response was seen across participants treated with JNT-517 irrespective of baseline blood Phe levels, which ranged from 593µM to 1,526µM with a mean of 1,124µM.
• A rapid onset of effect was observed with significant blood Phe reduction achieved within seven days after commencing dosing, which was sustained through the full 28 days of dosing.
• JNT-517 was safe and well tolerated with no serious adverse events and no clinically significant changes in laboratory parameters, consistent with the safety profile demonstrated in the Phase 1a healthy volunteer study.

“JNT-517 represents a completely new therapeutic approach that could transform the current treatment paradigm in PKU, in particular for individuals with severe, or classical, PKU where there is the highest unmet medical need,” said Cary O. Harding, MD, study investigator and Professor of Molecular and Medical Genetics at Oregon Health and Science University School of Medicine. “I am encouraged by the clinical results to date and look forward to working with Jnana and the PKU community to continue to advance this program.”

Based on these interim results, Jnana has adapted the protocol of the ongoing trial to include dose exploration. Jnana expects topline data from the second dose cohort in mid-2024 and plans to submit full data from the two dose cohorts for presentation at a scientific meeting in the second half of 2024. Jnana anticipates the company will engage regulators in the second half of 2024 and seek to advance JNT-517 directly into a pivotal Phase 3 study in the first half of 2025.

The ongoing clinical program includes a randomized, double-blind, placebo-controlled trial evaluating the safety, tolerability, pharmacokinetics, and effect on blood and urinary Phe of JNT-517 dosed over a four-week period in individuals diagnosed with PKU. The study dosed its first participant with PKU in August 2023 and is enrolling individuals aged 18 to 65 at clinical sites in the United States and Australia. For more information about the study, please see clinicaltrials.gov (NCT05781399).

JNT-517 is a selective small molecule inhibitor of the Phe transporter SLC6A19 that has the potential to be a first-in-class oral therapy used to treat any person with PKU, regardless of age or genotype. JNT-517 acts at a novel, cryptic allosteric site to block kidney reabsorption of Phe and offers a promising new approach to reduce blood Phe levels. The U.S. Food and Drug Administration granted JNT-517 Rare Pediatric Disease Designation in late 2022.

PKU is a rare inherited metabolic disorder caused by a deficiency of the enzyme phenylalanine hydroxylase (PAH). This enzyme is required for the breakdown of phenylalanine (Phe), an amino acid found in all protein-containing foods. When PAH is deficient or defective, Phe accumulates to abnormally high levels in the blood. If left untreated, toxic levels of Phe in the blood can result in progressive and severe neurological impairment and neuropsychological complications. The SLC transporter SLC6A19 is responsible for kidney reabsorption of Phe back into the bloodstream, and the inhibition of SLC6A19 offers a novel, oral approach for the treatment of PKU by facilitating urinary excretion of excess Phe.

Jnana Therapeutics is a clinical-stage biotechnology company leveraging its next-generation RAPID chemoproteomics platform to discover medicines for highly validated, challenging-to-drug targets to treat diseases with high unmet needs. Jnana is focused on developing first- and best-in-class therapies to treat a wide range of diseases, including rare diseases and immune-mediated diseases. Jnana’s wholly owned lead program, JNT-517, which targets an allosteric site on the phenylalanine transporter SLC6A19, is a potential first-in-class oral approach for the treatment of PKU, a rare genetic metabolic disease. Located in Boston, Jnana brings together scientific leaders in small molecule drug discovery and development, a highly experienced management team, and the backing of leading life science investors Bain Capital Life Sciences, RA Capital Management, Polaris Partners, Versant Ventures, Avalon Ventures, Pfizer Ventures, and AbbVie Ventures. For more information, visit www.jnanatx.com.