Correction to: Safety, Tolerability, and Pharmacokinetics of GDC-0276, a Novel NaV1.7 Inhibitor, in a First-in-Human, Single- and Multiple-Dose Study in Healthy Volunteers.

The original version of this article unfortunately contained a mistake. A few entries were incorrect in Table 2.

Safety, Tolerability, and Pharmacokinetics of GDC-0276, a Novel NaV1.7 Inhibitor, in a First-in-Human, Single- and Multiple-Dose Study in Healthy Volunteers.

BACKGROUND AND OBJECTIVE: Current pain therapies often do not provide adequate pain relief and have dose-limiting adverse effects. Genetic evidence indicates that NaV1.7 sodium channels are required for pain transduction and therefore represent an important therapeutic target. GDC-0276 is a novel NaV1.7 inhibitor developed for the treatment of pain. This first-in-human trial evaluated the safety, tolerability, and pharmacokinetics of orally administered GDC-0276 in healthy subjects. METHODS: This phase I, randomized, double-blind, placebo-controlled study assessed GDC-0276 as powder-in-capsule (PIC) or cyclodextrin solution (CD) single doses (SDs) of 2-270 mg (seven cohorts) and 45-540 mg (five cohorts), respectively. Multiple (MD) PIC doses were administered as total daily doses of 15-540 mg divided into two or three doses/day, up to 10 or 14 days. Safety was assessed by monitoring adverse events (AEs), vital signs, physical examinations, electrocardiograms, and laboratory tests for up to 15 days after the last day of dosing. GDC-0276 plasma pharmacokinetics were also determined. RESULTS: Three stages included 183 randomized subjects. GDC-0276 plasma exposure increased with dose level for all stages. Exposure was higher in the SD-CD cohorts compared with the equivalent SD-PIC dose levels. SDs were adequately tolerated up to 270 mg (SD-PIC) and 360 mg (SD-CD). Hypotension limited tolerability in the 540-mg SD-CD cohort. Multiple PIC doses were tolerated up to 270 mg twice daily, however liver transaminase elevations were frequently observed. No deaths or serious AEs occurred. CONCLUSION: GDC-0276 exhibited a safety and pharmacokinetic profile that supports its future investigation as a potential therapeutic for pain.

Small molecule inhibition of GDC-0449 refractory smoothened mutants and downstream mechanisms of drug resistance.

Inappropriate Hedgehog (Hh) signaling has been directly linked to medulloblastoma (MB), a common malignant brain tumor in children. GDC-0449 is an Hh pathway inhibitor (HPI) currently under clinical investigation as an anticancer agent. Treatment of a MB patient with GDC-0449 initially regressed tumors, but this individual ultimately relapsed with a D473H resistance mutation in Smoothened (SMO), the molecular target of GDC-0449. To explore the role of the mutated aspartic acid residue in SMO function, we substituted D473 with every amino acid and found that all functional mutants were resistant to GDC-0449, with positively charged residues conferring potential oncogenic properties. Alanine scan mutagenesis of SMO further identified E518 as a novel prospective mutation site for GDC-0449 resistance. To overcome this form of acquired resistance, we screened a panel of chemically diverse HPIs and identified several antagonists with potent in vitro activity against these GDC-0449-resistant SMO mutants. The bis-amide compound 5 was of particular interest, as it was able to inhibit tumor growth mediated by drug resistant SMO in a murine allograft model of MB. However, focal amplifications of the Hh pathway transcription factor Gli2 and the Hh target gene cyclin D1 (Ccnd1) were observed in two additional resistant models, indicating that resistance may also occur downstream of SMO. Importantly, these HPI resistant MB allografts retained their sensitivity to PI3K inhibition, presenting additional opportunities for the treatment of such tumors.

Synthesis and structure-activity relationship of N-acyl-Gly-, N-acyl-Sar- and N-blocked-boroPro inhibitors of FAP, DPP4, and POP.

The structure-activity relationship of various N-acyl-Gly-, N-acyl-Sar-, and N-blocked-boroPro derivatives against three prolyl peptidases was explored. Several N-acyl-Gly- and N-blocked-boroPro compounds showed low nanomolar inhibitory activity against fibroblast activation protein (FAP) and prolyl oligopeptidase (POP) and selectivity against dipeptidyl peptidase-4 (DPP4). N-Acyl-Sar-boroPro analogs retained selectivity against DPP4 and potent POP inhibitory activity but displayed decreased FAP inhibitory activity.

Selective inhibition of fibroblast activation protein protease based on dipeptide substrate specificity.

Fibroblast activation protein (FAP) is a transmembrane serine peptidase that belongs to the prolyl peptidase family. FAP has been implicated in cancer; however, its specific role remains elusive because inhibitors that distinguish FAP from other prolyl peptidases like dipeptidyl peptidase-4 (DPP-4) have not been developed. To identify peptide motifs for FAP-selective inhibitor design, we used P(2)-Pro(1) and acetyl (Ac)-P(2)-Pro(1) dipeptide substrate libraries, where P(2) was varied and substrate hydrolysis occurs between Pro(1) and a fluorescent leaving group. With the P(2)-Pro(1) library, FAP preferred Ile, Pro, or Arg at the P(2) residue; however, DPP-4 showed broad reactivity against this library, precluding selectivity. By contrast, with the Ac-P(2)-Pro(1) library, FAP cleaved only Ac-Gly-Pro, whereas DPP-4 showed little reactivity with all substrates. FAP also cleaved formyl-, benzyloxycarbonyl-, biotinyl-, and peptidyl-Gly-Pro substrates, which DPP-4 cleaved poorly, suggesting an N-acyl-Gly-Pro motif for inhibitor design. Therefore, we synthesized and tested the compound Ac-Gly-prolineboronic acid, which inhibited FAP with a K(i) of 23 +/- 3 nm. This was approximately 9- to approximately 5400-fold lower than the K(i) values for other prolyl peptidases, including DPP-4, DPP-7, DPP-8, DPP-9, prolyl oligopeptidase, and acylpeptide hydrolase. These results identify Ac-Gly-BoroPro as a FAP-selective inhibitor and suggest that N-acyl-Gly-Pro-based inhibitors will allow testing of FAP as a therapeutic target.

Inhibition and reversal of myogenic differentiation by purine-based microtubule assembly inhibitors.

Using a muscle cell differentiation screen, we have identified myoseverin from a 2,6,9-trisubsituted purine library as a purine-based microtubule binding molecule [1]. Structure-activity relation studies of myoseverin identify positions N2 and N6 to be critical for inhibiting muscle differentiation. Inhibition of microtubule polymerization induced the reversion of terminally differentiated myotubes to mononucleated cells that were responsive to both growth and differentiation conditions, without any observable cytotoxicity. Comparison of myoseverin derivatives to taxol, vinblastine, nocodazole, and colchicine identify myoseverin's effect as being selectively reversible in addition to lacking the cytotoxic effects of these non-purine-based microtubule-disrupting molecules. Myoseverin, as a purine-based microtubule inhibitor, reverted terminal muscle-differentiated cells to a state that was responsive to environmental cues. These results suggest that myoseverin may have applications in muscle regeneration and stem cell differentiation.