THN102

Theranexus's now-discontinued fixed-dose combination of modafinil + sub-antiarrhythmic flecainide. Mechanism is genuinely interesting (flecainide blocks astrocytic Cx30 gap junctions to amplify modafinil's wake signal). One sleep-deprivation study in 20 healthy men showed superiority over modafinil alone. But narcolepsy Phase 2 missed primary endpoint, only the Parkinson's Phase 2a hit (low dose only), Theranexus shut the program down in 2022, and the company (now THX Pharma) is wholly focused on Batten disease as of 2024-2025. Not commercially available, not buyable on gray market. For Dylan: SKIP — modafinil monotherapy already does the job and adding a class IC antiarrhythmic without cardiac monitoring is poor risk/reward at age 20.

THN102's premise is mechanistically novel and worth understanding even though the program is dead.

Modafinil component (the wake driver): Standard modafinil. Weak DAT inhibition → indirect orexin/histamine cascade → cortical wakefulness without classical-stimulant sympathetic load. Full mechanism in [modafinil.md].

Flecainide component (the Cx30 modulator — the actual innovation):

• Flecainide is a Vaughan-Williams class IC sodium channel blocker, FDA-approved 1985 as an oral antiarrhythmic for paroxysmal atrial fibrillation and PSVT.
• At antiarrhythmic doses (100-400 mg/d) it blocks cardiac Nav1.5. At THN102 doses (2-27 mg/d), it is sub-antiarrhythmic and acts on a completely different target: astrocytic connexin 30 (Cx30) gap junctions in the CNS.
• Why astrocyte gap junctions matter for modafinil: Duchêne et al. and Liu et al. (2013, 2016) showed that modafinil itself raises Cx30 expression in cortical astrocytes — i.e., modafinil "over-couples" the astrocyte network. The Sleep 2016 commentary (Bjorness & Greene) reframed this: astrocyte over-coupling actually inhibits modafinil's wake-promoting effects, and partially blocking Cx30 with flecainide restores functional glial network organization.
• Net effect: Co-administration of low-dose flecainide with modafinil produced synergistic wake/cognitive enhancement at sub-effective doses of either drug alone in mouse models — the rationale for the human program.

What flecainide does NOT do here:

• Does not change modafinil plasma or brain levels (verified in the Theranexus PK studies).
• Does not act via cardiac sodium channels at the THN102 doses tested.
• Does not affect Cx43 (the other major astroglial connexin) — selectivity for Cx30 is the design feature.

Why this matters mechanistically: It's the first clinical attempt to therapeutically modulate the glial side of a neuro-glial drug interaction. Even if THN102 itself died, the framework (Theranexus's "neuroglial" combination strategy) influenced thinking about sleep neurobiology and is reflected in Theranexus's other programs (THN201 = donepezil + mefloquine for Alzheimer's, also discontinued).