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The psychedelic compound psilocybin has shown therapeutic benefit in the treatment of numerous psychiatric diseases. A recent randomized clinical trial conducted at Johns Hopkins Bayview Medical Center demonstrated the efficacy of psilocybin-assisted therapy in the treatment of Major Depressive Disorder (MDD). Similarly, a phase IIb study evaluating psilocybin-assisted therapy for treatment-resistant depression (TRD) presented statistically meaningful and long-term reduction in depressive symptoms. Also, many studies have reported the successful treatment of severe anxiety after a single oral dose of psilocybin, especially in patients struggling with cancer-related distress (CRD). Despite these compelling clinical results, concerns regarding the duration of the psychedelic experience produced by psilocybin pose a significant barrier to its widespread therapeutic application. Psilocybin, derived from magic mushrooms is the naturally occurring prodrug of the neuroactive compound psilocin. When orally administered, exposure to the acidic gastrointestinal (GI) environment together with enzymatic processing by intestinal and hepatic alkaline phosphatase lead to the dephosphorylation of psilocybin producing elevated levels of systemic psilocin. These plasma levels are detectable up to 24 h and produce a psychoactive episode lasting as long as 6 h post-ingestion. In order to positively modify the kinetics of the acute psychedelic response, we have engineered a library of novel prodrug derivatives (NPDs) of psilocin, introducing a diversity of alternative metabolically cleavable moieties modified at the 4-carbon position of the core indole ring. This library consists of twenty-eight unique compounds represented by nine distinct prodrug classes. Each molecule was screenedin vitrofor metabolic stability using isolated human serum, and human cellular fractions derived from liver and intestinal tissues. This screen revealed fifteen prodrugs that produced measurable levels of psilocinin vitro, with ester and thiocarbonate-based prodrug derivatives significantly represented. These fifteen NPDs were further evaluated for pharmacokinetic (PK) profiles in mice, assessing plasma levels of both residual prodrug and resultant psilocin. PK results confirmed the efficiency of ester and thiocarbonate-based prodrug metabolism upon oral and intravenous administration, achieving levels reduced, albeit comparable to levels of psilocybin-derived psilocin. Of note, almost all NPDs tested maintained reduced overall exposure of psilocin relative to psilocybin, with no measurable levels detected at 24 h post-dose. Finally, all NPDs were screened for CNS bioavailability in healthy mice using the Head Twitch Response (HTR), a behavioural biomarker of 5-HT2Areceptor stimulation and an established proxy for psychoactive potential. Interestingly, five NPDs produced peak HTR that approached or exceeded levels induced by an equivalent dose of psilocybin. Among these bioactive prodrugs, an ester-based and thiocarbonate-based molecule produced long-term anxiolytic benefit in chronically stressed mice evaluated in the marble burying psychiatric model. Overall, this screening campaign identified novel candidate prodrugs of psilocin with altered metabolic profiles and reduced pharmacological exposure, potentially attenuating the duration of the psychedelic response. These molecules still maintained the long-term psychiatric and physiological benefits characteristic of psilocybin therapy. Additionally, these modified parameters also offer the opportunity for altered routes of administration bypassing conventional oral dosing.

Targeted cancer therapy represents a paradigm-shifting approach that aims to deliver a toxic payload selectively to target-expressing cells thereby sparing normal tissues the off-target effects associated with traditional chemotherapeutics. Since most targeted constructs rely on standard microtubule inhibitors or DNA-reactive molecules as payloads, new toxins that inhibit other intracellular targets are needed to realize the full potential of targeted therapy. Among these new payloads, α-amanitin has gained attraction as a payload in targeted therapy. Here, we conjugate two synthetic amanitins at different sites to demonstrate their utility as payloads in peptide drug conjugates (PDCs). As an exemplary targeting agent, we chose octreotate, a well-studied somatostatin receptor (sstr2) peptide agonist for the conjugation to synthetic amatoxins via three tailor-built linkers. The linker chemistry permitted the evaluation of one non-cleavable and two cleavable self-immolative conjugates. The immolating linkers were chosen to take advantage of either the reducing potential of the intracellular environment or the high levels of lysosomal proteases in tumor cells to trigger toxin release. Cell-based assays on target-positive Ar42J cells revealed target-specific reduction in viability with up to 1000-fold enhancement in bioactivity compared to the untargeted amatoxins. Altogether, this preliminary study enabled the development of a highly modular synthetic platform for the construction of amanitin-based conjugates that can be readily extended to various targeting moieties., Synthetic amanitin is conjugated to octreotate as a targeting agent: three different linkers and two sites of attachment highlight a robust chemical approach leading to targeted cytotoxicity.

Alpha-amanitin, an extremely toxic bicyclic octapeptide extracted from the death-cap mushroom, Amanita phalloides, is a highly selective allosteric inhibitor of RNA polymerase II. Following on growing interest in using this toxin as a payload in antibody-drug conjugates, herein we report the synthesis and biochemical evaluation of several new derivatives of this toxin to probe the role of the trans-hydroxyproline (Hyp), which is known to be critical for toxicity. This structure activity relationship (SAR) study represents the first of its kind to use various Hyp-analogs to alter the conformational and H-bonding properties of Hyp in amanitin.

Here we report a scalable synthesis of the key amino acid residue, (2S,3R,4R)-4,5-dihydroxyisoleucine (DHIle) in α-amanitin, that in turn enables the scalable synthesis of an equipotent analogue, Asn(N-ethylazide)-S,6'-dideoxy-α-amanitin, suitable for CuAAC conjugation to empower studies on therapeutic antibody-drug conjugates.

Amanitin is used extensively as a research tool to inhibit RNA Pol II thereby implicating its role in mRNA transcription. Recently, amanitin has gained traction as a toxic payload for targeted therapy. Here we report the first-ever photocaged amanitin analog, that is non-toxic and can be pre-loaded into cells. Light provides a means to inhibit RNA Pol II and provoke cell death on-demand.

Appreciating the need to access synthetic analogs of amanitin, here we report the synthesis of 5′-hydroxy-6′-deoxy-amanitin, a novel, rationally-designed bioactive analog and constitutional isomer of α-amanitin, that is anticipated to be used as a payload for antibody drug conjugates. In completing this synthesis, we meet the challenge of diastereoselective sulfoxidation by presenting two high-yielding and diastereoselective sulfoxidation approaches to afford the more toxic (R)-sulfoxide., Elucidating a highly diastereoselective sulfoxidation of S-deoxy-amanitin to afford α-amanitin and a more synthetically accessible analog of near-native toxicity.

Here we report a scalable synthesis of the key amino acid residue, (2

α-Amanitin is an extremely toxic bicyclic octapeptide isolated from the death-cap mushroom, Amanita phalloides. As a potent inhibitor of RNA polymerase II, α-amanitin is toxic to eukaryotic cells. Recent interest in α-amanitin arises from its promise as a payload for antibody-drug conjugates. For over 60 years, A. phalloides has been the only source of α-amanitin. Here we report a synthesis of α-amanitin, which surmounts the key challenges for installing the 6-hydroxy-tryptathionine sulfoxide bridge, enantioselective synthesis of (2 S,3 R,4 R)-4,5-dihydroxy-isoleucine, and diastereoselective sulfoxidation.

Alpha-amanitin is an exceedingly toxic, naturally occurring, bicyclic octapeptide that inhibits RNA polymerase and results in cellular and organismal death. Here we report the straightforward synthesis of an amanitin analogue that exhibited near-native toxicity. A pendant alkyne was readily installed to enable copper-catalyzed alkyne-azide cycloaddition (CuAAC) to azido-rhodamine and two azide-bearing versions of the RGD peptide. The fluorescent toxin analogue entered cells and provoked morphological changes consistent with cell death. The latter two conjugates are as toxic as the parent alkyne precursor, which demonstrates that conjugation does not diminish toxicity. In addition, we showed that toxicity depends on a single diastereomer of the unnatural amino acid, dihydroxyisoleucine (DHIle), at position 3. The convenient synthesis of a heptapeptide precursor now provides access to bioactive amanitin analogues that may be readily conjugated to biomolecules of interest.