Background

DNL151 is an orally available, brain-penetrant inhibitor of the leucine-rich repeat kinase 2 (LRRK2). It started out as a backup to Denali’s lead LRRK2 inhibitor, DNL201; but it is now is its lead candidate after development of DNL201 was stopped in 2020.

LRRK2, also known as Dardarin, is a large, multidomain protein containing serine and threonine kinase activity. Kinase-activating mutations in the LRRK2 gene are the most frequent cause of inherited PD (reviewed in Schneider and Alcalay, 2020). Other variants in the gene are associated with higher risk of sporadic PD, and there is some evidence for LRRK2 kinase activation in idiopathic PD (Di Maio et al., 2018). Increased LRRK2 kinase activity impairs vesicle trafficking and lysosome function, and promotes neuroinflammation, processes that contribute to PD pathology (see review by Taylor and Alessi, 2020; Shutinoski et al., 2019; Sep 2018 news). Several companies are pursing LRRK2 inhibitors for treating PD; Denali was the first to begin clinical testing. 

No preclinical data has been published on DNL151. However, reducing LRRK2 activity using other inhibitors or by genetic knockdown in rodent models of PD has been reported to reduce α-synuclein aggregation, neuroinflammation, and dopaminergic neuron loss (Daher et al., 2014; Daher et al., 2015).

Besides brain, LRRK2 is highly expressed in the lungs, kidneys, and spleen. Knockout or systemic inhibition of LRRK2 was found to change lung morphology in rats or macaque monkeys, possibly by affecting lysosomal function (Fuji et al., 2015). This raised safety concerns of systemic LRRK2 inhibition. Recent data confirmed that three different inhibitors caused an accumulation of large vacuoles in lung cells of treated monkeys; this response did not compromise lung function after two weeks of treatment, and the changes reversed after the drugs were stopped (Baptista et al., 2020). For a review of patents on LRRK2 inhibitors, see Ding and Ren, 2020.

Findings

In December 2017, Denali began Phase 1 dosing of DNL151 (press release) with a 186-participant trial in the Netherlands. A January 2020 press release announced that DNL151 met biomarker and safety goals after evaluation in 153 healthy volunteers. The majority of participants had no or mild AEs at all doses tested. DNL151 dose-dependently reduced LRRK2 kinase activity by up to 80 percent, based on measuring phosphorylation of LRRK2 and its substrate pRab10 in blood. Urine levels of the lipid BMP, a marker of lysosome dysfunction, were reduced, as well. Based on these safety, target, and pathway engagement data, the trial was expanded to higher doses. It finished in February 2021.

In July 2019, a Phase 1b safety study began in 34 people with Parkinson’s disease. Participants with or without an LRRK2 mutation were randomized to a low, middle, or high dose of DNL151 or placebo, taken daily for 28 days. The primary outcome comprises adverse events and laboratory tests, vital signs, electrocardiogram, or neurological exam. Secondary outcomes include plasma pharmacokinetics, drug concentration in the CSF, and LRRK2 and Rab10 phosphorylation in blood. The trial finished in December 2020, after enrolling 36 participants in eight centers in the U.S. and Europe. In a January 2021 press release, Denali stated that the trial met target and pathway engagement goals.

In August 2020, Denali announced it would advance clinical development of DNL151 in collaboration with Biogen (press release).

In 2021, the companies completed additional Phase 1 studies of the absorption, metabolism, excretion, and bioavailability of radiolabeled DNL151 after single or multiple doses in healthy subjects. In 2022, another Phase 1 compared the pharmacokinetics, safety, and tolerability of single or multiple doses in 84 healthy Japanese, Chinese, and Caucasian people.

In April 2022, the companies began Phase 2b with a trial in early stage Parkinson’s disease. The 640 participants are to receive 225 mg BIIB122 once daily or matching placebo tablets, for 48 to 144 weeks. The primary outcome of time to worsening in the Movement Disorder Society-Unified Parkinson’s Disease Rating scale parts II and III assesses mainly motor symptoms and function. Secondary outcomes are adverse events, and change from baseline MDS-UPDRS, and time to worsening in daily activities. The expected end date is August 2025.

In August 2022, a Phase 3 study began recruiting 400 people with early stage Parkinson’s and specific LRRK2 mutations, for a similar course of treatment for up to 180 weeks, against the same primary and secondary outcome measures. This trial is slated for completion in January 2031.

For details on DNL151 trials, see clinicaltrials.gov.