data + articles · 2 listed
newest 2020T-495 A Takeda M1 positive allosteric modulator built deliberately weak at amplifying acetylcholine, made to test whether a low cooperativity ceiling is what separates a procognitive effect from cholinergic side effects.
- Hundredfold margin between the procognitive dose and diarrhea in rats
- Reverses scopolamine-induced memory deficits
- Additive with donepezil at doses that are subeffective alone
- Reverses memory deficits in A53T alpha-synuclein mice, a model of Lewy body and Parkinson's dementia
- Clean across a 106-target off-target panel
- Diarrhea at a hundredfold multiple of the effective dose in rats
- Convulsion and salivation in one of six rats at 100 mg/kg
- Weak intrinsic agonist activity at high concentrations
- No human exposure and no clinical safety data
Overview
The most interesting compound in the M1 PAM literature for a reason that has nothing to do with whether it works. It exists to prove a design rule, and it does: potency was never the problem, cooperativity was. A field that reflexively optimizes for the biggest number produced a decade of modulators that gave people diarrhea, and the fix was to aim lower on purpose.
- An alpha value of 170 sounds unimpressive until the alternatives are lined up next to it; the high cooperativity reference T-662 sits at 1,786, and it improved memory and caused diarrhea at the very same dose.
- Subeffective doses of T-495 and donepezil together reversed scopolamine-induced memory deficits in rats, while the same pairing with MK-7622 did not, which suggests a high cooperativity modulator loses rather than gains when extra acetylcholine is put in front of it.
Mechanism
T-495 is a dihydrobenzoxazinone that potentiates at M1 with an inflection point of 2.3 nM in cells expressing the human receptor, while its inflection point at human M2 through M5 is above 1,000 nM; on its own it is only a weak , EC50 649 nM, leaving a 282-fold gap between modulation and direct activation [1]. The number the compound exists to test is cooperativity. Fitting the displacement of [3H]pirenzepine by to an ternary complex model gives T-495 an alpha value of 170, against 511 for the clinically tested MK-7622 and 1,786 for the high cooperativity reference T-662 [1].
Alpha is the ceiling on how far the modulator can raise 's affinity for the receptor, so a low alpha amplifies a signal that is already there without overriding its timing; a high alpha can flatten the spatial and temporal pattern that cortical acetylcholine release normally carries. The screening logic behind the choice came from earlier Takeda work showing that contraction of isolated ileum scales with a modulator's alpha value rather than with its potency [2].
receptor fingerprint
M1 (CHRM1)Positive Allosteric Modulator
M2 through M5 (CHRM2 to CHRM5)No potentiation
M1 (CHRM1), direct activationWeak Agonist
Safetyrisks and cautions, not medical advice
No human has received T-495 and no clinical safety data exist. In rats it caused no cholinergic signs at doses up to 30 mg/kg; at 100 mg/kg it raised diarrhea scores and produced convulsion and salivation in one of six animals, so the ceiling is real rather than absent [1]. Measured against the dose that reversed scopolamine-induced memory deficits, that is a hundredfold margin, where MK-7622 improved memory and induced diarrhea at the same dose [1].
Isolated mouse ileum makes the same point more directly: T-495 increased spontaneous contraction only at 1 micromolar, while MK-7622 did so at 0.01 micromolar, the lowest concentration tested [1]. A screen of 106 receptors, enzymes, ion channels and transporters at 10 micromolar returned only two hits, 76 percent inhibition at the imidazoline I2 receptor and 58 percent at the dopamine transporter [1]. The convulsion seen at the top dose matters, because seizure has ended other M1 PAM programs, and a single event in six rats is a signal rather than a measurement.
History
Synthesized at Takeda Pharmaceutical Company in Fujisawa, Japan, and characterized in the 2020 report by Mandai and colleagues, which cites patent WO2016208775, example 24, as the route [1]. It came after TAK-071, the low cooperativity modulator from the same program that Takeda carried into clinical trials, and was profiled head to head against MK-7622 as the high cooperativity control. Takeda's published account frames T-495 as a second demonstration of the cooperativity principle rather than as a development candidate.
Reputation
Known to the muscarinic allosteric field and almost nowhere else. Its standing rests on one number and one comparison: a modulator can be made weaker on purpose and come out ahead, which is an unusual argument in a discipline that normally treats potency as the score. The side by side profile against MK-7622 is the clearest published account of why the first generation of M1 PAMs disappointed on tolerability.
Subjective profileweighing the evidence above
The most interesting compound in the M1 PAM literature for a reason that has nothing to do with whether it works. It exists to prove a design rule, and it does: potency was never the problem, cooperativity was. A field that reflexively optimizes for the biggest number produced a decade of modulators that gave people diarrhea, and the fix was to aim lower on purpose.
Resources
This entry is here for reference.
Research
- 1.T-495, a novel low cooperative M1 receptor positive allosteric modulator, improves memory deficits associated with cholinergic dysfunction and is characterized by low gastrointestinal side effect risk
- 2.An Approach to Discovering Novel Muscarinic M1 Receptor Positive Allosteric Modulators with Potent Cognitive Improvement and Minimized Gastrointestinal Dysfunction
2 listed here; entry last updated July 2026
Reviews
My notesprivate to this device
FAQ
Why would anyone deliberately design a weaker modulator?
Because the gut uses the same receptor. Cooperativity sets how far a modulator can strengthen acetylcholine's grip on M1, and enteric motility responds to that push more steeply than cognition does. A low ceiling still lifts the cortical signal, which is faint and benefits from help, but never lifts the enteric signal, which is already robust, past the point where it produces diarrhea.
Is T-495 the same thing as TAK-071?
No. They are separate Takeda molecules from the same program. TAK-071 has an alpha value of 199 and went into clinical trials; T-495 has an alpha value of 170 and was characterized preclinically as a further test of the same design rule.
What does the alpha value actually measure?
It is the cooperativity factor from the allosteric ternary complex model: the maximum fold increase in acetylcholine's affinity for M1 that the modulator can produce, no matter how much modulator is present. It is a ceiling, not a dose response, which is why it can be compared across compounds.
Can I take it?
No. There is no human dose, no formulation and no clinical data. T-495 exists as a laboratory compound.
Adverse effects
- Diarrhea at a hundredfold multiple of the effective dose in rats
- Convulsion and salivation in one of six rats at 100 mg/kg
- Weak intrinsic agonist activity at high concentrations
- No human exposure and no clinical safety data