Two randomized, double-blind, placebo-controlled, dose-escalation phase 1 studies evaluating BTH1677, a 1, 3-1,6 beta glucan pathogen associated molecular pattern, in healthy volunteer subjects

BACKGROUND

BTH1677 is a beta glucan pathogen associated molecular pattern (PAMP) currently being investigated as a novel cancer therapy. Here, the initial safety and pharmacokinetic (PK) results of BTH1677 in healthy subjects are reported.

SUBJECTS AND METHODS

In the Phase 1a single-dosing study, subjects were randomized (3:1 per cohort) to a single intravenous (i.v.) infusion of BTH1677 at 0.5, 1, 2, 4, or 6 mg/kg or placebo, respectively. In the Phase 1b multi-dosing study, subjects were randomized (3:1 per cohort) to 7 daily i.v. infusions of BTH1677 at 1, 2, or 4 mg/kg or placebo, respectively. Safety and PK non-compartmental analyses were performed.

RESULTS

Thirty-six subjects (N = 24 Phase 1a; N = 12 Phase 1b) were randomized to treatment. No deaths or serious adverse events occurred in either study. Mild or moderate adverse events (AEs) occurred in 67% of BTH1677-treated subjects in both studies. Treatment-related AEs (occurring in ≥10% of subjects) included dyspnea, flushing, headache, nausea, paraesthesia, and rash in Phase 1a and conjunctivitis and headache in Phase 1b. BTH1677 serum concentration was linear with dose. Clearance, serum elimination half-life (t1/2) and volume of distribution (Vss) were BTH1677 dose-independent. In Phase 1b, area under the curve, t1/2, and Vss values were larger at steady state on days 6-30 versus day 0.

CONCLUSIONS

BTH1677 was well tolerated after single doses up to 6 mg/kg and after 7 daily doses up to 4 mg/kg.

Crystal structure of the leucine-rich repeat domain of the NOD-like receptor NLRP1: implications for binding of muramyl dipeptide

The NOD-like receptor NLRP1 (NLR family, pyrin domain containing 1) senses the presence of the bacterial cell wall component l-muramyl dipeptide (MDP) inside the cell. We determined the crystal structure of the LRR domain of human NLRP1 in the absence of MDP to a resolution of 1.65Å. The fold of the structure can be assigned to the ribonuclease inhibitor-like class of LRR proteins. We compared our structure with X-ray models of the LRR domains of NLRX1 and NLRC4 and a homology model of the LRR domain of NOD2. We conclude that the MDP binding site of NLRP1 is not located in the LRR domain.