Cassava Sciences : TSCA Cassava June 26 2025

Published: 2025-06-30 07:01:07 ET SAVA

Published on 06/30/2025 at 07:01

‌None of the serious adverse events reported by patients (n=237) in the two double-blind phase 3 studies or any other clinical study were assessed as study-drug related

1Cassava Sciences, Inc, Austin, TX and 2Department of Neurosurgery, Yale School of Medicine, New Haven, CT

1. An unbiased screen identified increased Filamin A (FLNA) in TSC and FCDII mouse

models and human brain tissue

Human FCD2 tissue

An unbiased screen (PCR array) identified 5/84 dysregulated genes including Flna in the brain of Tsc1 KO mice (not shown).

We validated that FLNA is elevated at the protein level in the brain of

Tsc1 cKO mice (not shown) and RhebCA mice.

We and others validated that FLNA is increased in FCD2 and TSC (not shown) cortical tissue

RhebCA mice

Abstract

Epilepsy treatments for patients with mechanistic target of rapamycin (mTOR) disorders, such as tuberous sclerosis complex (TSC) or focal cortical dysplasia type II (FCDII), are urgently needed. In these patients, the presence of focal cortical malformations is associated with the occurrence of lifelong epilepsy, leading to severe neurological comorbidities. Recent evidence suggests that expression of the actin cross-linking protein filamin A (FLNA) is increased in resected cortical tissue from patients with TSC and FCDII, and in experimental cortical malformations leading to focal onset seizures in mice.

Restoring proper FLNA expression in dysmorphic neurons in the focal cortical malformation reduced soma overgrowth and seizure activity. Treating mice with simufilam, a small molecule thought to modulate FLNA function, either before or after seizure onset, alleviated neuronal abnormalities and reduced seizure activity compared to vehicle-treated mice. Similarly preclinical studies are underway with the TSC Alliance preclinical consortium using conditional Tsc1 knockout (cKO) mice. Simufilam shows high brain permeability in mice and rats and was measurable in CSF from human volunteers. Chronic oral toxicology studies found no adverse effects at doses up to 50 mg/kg/day in rats and 1250 mg/kg/day in mice. In two double-blind phase 3 studies in patients with mild-to-moderate Alzheimer's disease (n=1,929), simufilam demonstrated a favorable safety profile. Non-serious adverse events were typically mild and not considered study-drug related, and no specific adverse event was associated with simufilam administration. None of the reported serious adverse events in phase 3 (n=237) or any other clinical study were assessed as study-drug related. Based on these findings, Cassava Sciences, Inc. is preparing to submit an IND application to the FDA and enroll patients in a clinical trial of simufilam for the treatment of epilepsy in TSC

4. Simufilam is a small molecule with high brain permeability and an excellent safety profile

FLNA nuclei

Control RhebCAneurons Vehicle Vehicle Simufilam

Single dose in healthy volunteers 18-46 yo 1,929 enrolled AD subjects for 76 weeks

Simufilam 50 mg bid

N = 376

Simufilam 100 mg bid

N = 773

Placebo N = 771

Any Adverse Event (AE)

288 (76.6%)

570 (73.7%)

551 (71.5%)

AE Assessed by Investigator as Related

to Study Drug

50 (13.3%)

138 (17.9%)

102 (13.2%)

Serious Adverse Event

61 (16.2%)

95 (12.3%)

81 (10.5%)

Death

6 (1.6%)

3 (0.4%)

6 (0.8%)

AE Leading to Study Discontinuation

34 (9.0%)

58 (7.5%)

34 (4.4%)

Half-life at 100 mg single dose in healthy volunteers was 4.45 hrs

CSF/plasma ratio was 0.61 (0.41 SD) in Alzheimer's disease (AD) patients following 100 mg BID for 28 days (not shown)

Simufilam was safe and well-tolerated. There were no serious adverse events, and no adverse events were related to 10 mg BID simufilam in

(mice)

3. Reducing FLNA levels limited cell overgrowth and seizure activity

Reduction in seizure activity

Reduction in cell overgrowth

A short-hairpin (sh) RNA was expressed to reduce FLNA expression in RhebCA-expressing neurons. Flna shRNA reduced cell overgrowth compared to control shRNA (against luciferase) and significantly reduced tonic-clonic seizure activity. P = postnatal day

Control (GFP) RhebCA RhebCA + Flna shRNA

Number of seizures per day

Number of seizures per day

>1,929 AD patients

FLNA is a large multi-functional protein inside cells and its increased expression in

TSC is mTOR-independent

In Tsc1 cKO mice

FLNA is an actin crosslinking molecule with dozens of binding partners, acting as a platform inside cells that regulates the function of its binding partners and the shape of the cytoskeleton

FLNA controls many aspects of cell development

The increase in FLNA is mTOR-independent

Increased FLNA preceded seizure onset and may thus contribute to the development of a circuitry prone to seizures

Vehicle 12 mg/kg simufilam or vehicle

References

Convulsive seizures from experimental focal cortical dysplasia occur independently of cell misplacement. Hsieh LS et al. 2016 Nat. Comms 7:11753.

MEK-ERK1/2-dependent FLNA overexpression promotes abnormal dendritic patterning in tuberous sclerosis independent of mTOR. Zhang L, et al. 2014. Neuron 84:78.

Filamin A inhibition reduces seizure activity in a mouse model of focal cortical malformations. Zhang L, et al. 2020 Sci. Trans. Med. 12:eaay0289.

Acknowledgements and COI

The work was funded by NIH/NINDS and DoD grants (Bordey) and Cassava Sciences.

Dr. Bordey is a professor at Yale and an employee of Cassava Sciences since 2025.

1 dose:

12 mg/kg (salt), intraperitoneal, BID

3 treatment ages: Neonate (P8-P66), Young adult (P29-P54), Adult (P61) Treatment length: >3 weeks (analysis of seizures during 5 last treatment days Video-EEG: 5 days at the end of treatment or continuous (adult group)

Control groups: Vehicle (saline) for each

5. Simufilam reduced cell overgrowth and seizure activity in RhebCA mice

Reduction in cell overgrowth

60% reduction in seizure frequency

6. Simufilam's effect takes time to reduce seizure activity in RhebCA mice

Baseline

Treatment

IUE RhebCA

Vehicle

Vehicle

Mice

D1-D5

Vehicle

Simufilam

D27-D31

Mice

D6-D12

D39-D45

Vehicle Vehicle-to-Simufilam

Seizures were recorded from P61 to P92 (vehicle) or to P106 (drug)

Seizure activity increased over time (5 last days vs first 5 days) in vehicle-treated mice consistent with an increase in cell overgrowth and network abnormalities

Simufilam alleviated the increase in seizure activity observed in vehicle treated mice

Simufilam significantly reduced seizure activity when comparing the last 5 days of treatment to the 5 days preceding treatment (baseline phase)

Conclusion

Mutant

TSC1/TSC2

Increased

Rheb

Everolimus

Simufilam (PTI-125)

Increased

mTOR

Increased

Filamin A

Cell overgrowth,

brain malformations

Seizures

Diagram illustrating our findings and hypothesis

Transgenic mice with conditional Tsc1 deletion (cKO, Emx1 promoter)

Widespread forebrain (pyramidal neurons and astrocytes) abnormalities Spontaneous seizures

Mouse models

Cortical tubers in humans

Tsc1 cKO mice

Loss of Function mutations

RhebCA mice

In utero expression of a constitutively active Rheb

Cortical tuber-like malformation Spontaneous seizures

Focal onset as seen in patients

Protein synthesis Cell growth

Tonic-clonic seizures

We used both transgenic conditional Tsc1 KO mice (Emx1-Cre x Tsc1fl/-) and constitutively active Rheb (RhebCA) mice. These display a focal cortical malformation generated using in utero electroporation (IUE) resulting in spontaneous seizures. Seizures were recorded using video-EEG (Pinnacle system) and tonic clonic seizures were quantified.

Disclaimer

Cassava Sciences Inc. published this content on June 30, 2025, and is solely responsible for the information contained herein. Distributed via Public Technologies (PUBT), unedited and unaltered, on June 30, 2025 at 11:00 UTC.