CDKL5 deficiency disorder: 2026 so far

Attention moved from early response to how long benefits last.

In the months covered, the main human treatment update was a small open-label report (a study where everyone gets the treatment, with no comparison group). In that report, adding highly purified cannabidiol (CBD) was linked to strong early seizure reductions, but the effect was less consistent with longer follow-up. Fewer children kept the same seizure-reduction threshold at 6 months. Only a small minority did at 12 months. In that dataset, this suggests seizure response may fade for many over time. Side effects were common but described as not serious in the report, and one participant stopped CBD due to a skin rash. This helps set expectations that CBD response may change over time for some people, rather than staying the same for everyone.

Research covered in: February 2026

Reports described real-world symptom patterns beyond baseline seizures.

Two large caregiver-reported datasets highlighted that daily patterns in CDD can vary and may occur alongside other symptoms. One database analysis described several types of sleep difficulty, including trouble falling asleep, night waking, daytime sleepiness, and breathing-related symptoms. It also reported that sleep problems were more often reported alongside factors such as seizure patterns, constipation, and behavioral symptoms, without showing cause-and-effect. Separately, a retrospective survey (a look back at past experiences) reported that many respondents observed fewer seizures during febrile illnesses (illnesses with fever). Some also reported seizure reduction lasting days to weeks afterward. In that survey, there was no clear link to specific clinical or genetic features. These reports mainly give clearer descriptions of common but variable real-world patterns that can affect quality of life and how symptoms get tracked in studies.

Research covered in: January 2026, August 2026

EEG work shifted from severity correlation to timing details in development.

In the months covered, EEG (a brain-wave test) research moved from identifying severity-linked resting EEG features to mapping how EEG changes unfold in early life. A multi-site study reported that resting EEG background slowing measures tracked with clinical severity in a CDD group. In the same study, visual and auditory evoked potentials (EEG responses to sights or sounds) did not show a meaningful relationship to severity. A separate retrospective cohort of infants and young children described EEG background activity becoming more abnormal across the first 2 years of life. It also reported that several EEG features were linked with lower developmental scores in their analyses. Together, this supports resting EEG background activity as a research marker that may reflect overall severity and early developmental burden, while still not proving it predicts any one child's future or that changing EEG changes outcomes.

Research covered in: August 2026, September 2026

Measurement studies clarified what can show change, and what may not.

In the months covered, several reports examined whether commonly used study measures can detect meaningful change in CDD. A large international study found a floor effect (many participants scored at the bottom) on the GMFM-88 motor scale, suggesting it may fail to detect improvement. In contrast, caregiver-reported daily functioning (Vineland-3) and development testing (Bayley-4) were described as feasible and sometimes showed age-related gains in specific domains. Separate focus-group work in Lennox-Gastaut syndrome, rather than specifically in CDD, reported that some commonly used questionnaires can miss daily-life issues such as sleep, digestion, safety, and caregiver burden and may not capture nonverbal or alternative communication well. This mainly influences how future studies choose what to measure, and how well research results reflect daily functioning beyond seizures.

Research covered in: January 2026, August 2026

Several lab and mouse approaches were reported, but not tested in people.

So far in 2026, several possible disease-modifying strategies were reported only in cells, organoids (mini lab-grown tissue models), or mouse models, without evidence in people. These included base editing (a type of gene editing) in patient-derived cells reported to restore CDKL5 expression and improve neuron-related lab readouts. They also included an organoid gene-therapy delivery strategy designed to spread CDKL5 to nearby cells. Mouse studies targeted pathways such as KCC2 activation (OV350) or increasing 2-AG signaling (MAGL inhibitor JZL184). Those mouse findings were mixed or limited, depending on which outcome was measured. Additional mechanistic work linked CDKL5 loss to circuit-specific changes, including sensory-circuit findings and diffusion MRI (a scan that maps brain connections) connectivity differences in mice. It also linked CDKL5 loss to intracellular transport changes along microtubules (cell structures that help move materials) in mouse and neuron experiments. These studies mainly point to candidate approaches and lab measurements for future testing, but they do not show safety or benefit in children or adults with CDD.

Research covered in: February 2026, March 2026, April 2026, May 2026, August 2026, September 2026