Inhalable spray-dried formulation of D-LAK antimicrobial peptides targeting tuberculosis

Abstract

Tuberculosis (TB) is a global disease that is becoming more difficult to treat due to the emergence of multidrug resistant (MDR) Mycobacterium tuberculosis. Inhalable antimicrobial peptides (AMPs) are potentially useful alternative anti-TB agents because they can overcome resistance against classical antibiotics, reduce systemic adverse effects, and achieve local targeting. The aims of the current study were to produce inhalable dry powders containing d-enantiomeric AMPs (D-LAK120-HP13 and D-LAK120-A) and evaluate their solid state properties, aerosol performance, and structural conformation. These two peptides were spray dried with mannitol as a bulking agent at three mass ratios (peptide:mannitol 1:99, 1:49, and 1:24) from aqueous solutions. The resultant particles were spherical, with those containing D-LAK120-HP13 being more corrugated than those with D-LAK120-A. The median volumetric diameter of the particles was approximately 3μm. The residual water content of all powders were <3% w/w and crystalline, due to the low hygroscopicity and crystallinity of mannitol, respectively. The mannitol changed from a mixture of alpha- and beta-forms to delta form with an increasing proportion of AMP in the formulation. The emitted fraction and fine particle fraction of the powders when dispersed from an Osmohaler(®) at 90L/min were about 80% and 50-60% of the loaded dose, respectively, indicating good aerosol performance. Circular dichroism data showed that D-LAK120-HP13 dissolved in Tris buffer at pH 7.15 was of a disordered conformation. In contrast, D-LAK120-A showed greater α-helical conformation. Since the conformations of the AMPs were comparable to the controls (unprocessed peptides), the spray drying process did not substantially affect their secondary structures. In conclusion, spray dried powders containing d-enantiomeric AMPs with preserved secondary molecular structures and good aerosol performance could be successfully produced. They may potentially be used for treating MDR-TB when delivered by inhalation.

Peptides with Dual Antimicrobial and Anticancer Activities

“…An example is the synthetic design of D-enantiomeric peptides, like DJK-5/6, which show improved activity against bacterial infections in in vivo models, comparable to that of the L-enantiomeric peptides, without showing any cytotoxic activity (de la Fuente-Núñez et al, 2015 ; Mansour et al, 2016 ). This type of peptide were also shown to be more actively effective against drug-resistant tuberculosis pathogens, and have already been tested with inhalable spray-dried formulations (Lan et al, 2014 ; Kwok et al, 2015 ). In terms of ACPs, SVS-1 was seen to be more effective, compared to its L-isomeric peptide form (Sinthuvanich et al, 2012 ).…”

Host Antimicrobial Peptides: The Promise of New Treatment Strategies against Tuberculosis

“…The peptides were designed to enhance their antimicrobial activity and decrease their hemolytic effect ( 188 ), providing efficient antimycobacterial activity at non-toxic concentrations. Furthermore, d -LAK peptides can be administered as inhalable dry powder ( 176 ). Another synthetic α-helical peptide, the M(LLKK)2M, was proven successful against MDR strains when combined with RIF ( 187 ).…”

Tribolium castaneum defensin 1 kills Moraxella catarrhalis in an in vitro infection model but does not harm commensal bacteria

“…With M. catarrhalis, we chose an important pathogen with potentially chronic disease manifestation, which we show for the first time to be sensitive to defensin 1 and sarcotoxin 1 C. The clinical implications of AMPs against pathogens of the airways necessitates development of topical application of AMPs to the lung epithelium, which requires the large-scale production of AMPs as aerosol formulations [24]. Recently, successful attempts have been made to neutralize Pseudomonas aeruginosa with AMPs coupled to nanoparticles in a mouse model [25], and also to render AMPs inhalable by spray-drying [26]. In the advent of spreading antibiotics resistance, AMPs hold great potential as successors or support of classical antibiotic treatment.…”