Mouse Model of Pneumocystis
1
www.ebmt.org #EBMT19 Melanie T. Cushion 1,2,3 , Taylor Sandison 4 , Alan Ashbaugh 1,2.3 1 University of Cincinnati, College of Medicine; 2 Veterans Affairs Medical Center, Research Service; 3 Cincinnati Education for Veterans Foundation, Cincinnati, OH; 4 Cidara Therapeutics, San Diego, CA, USA • Pneumocystis pneumonia (PCP) is an infection of the immunocompromised, and the risk of PCP warrants prophylaxis. Complications, such as myelosuppression, nephrotoxicity, and intolerance associated with the current standard of care, trimethoprim-sulfamethoxazole, (TMP/SMX) may hinder or interrupt prophylaxis. • Rezafungin (RZF) is a novel echinocandin in development for prevention of invasive fungal disease caused by Candida, Aspergillus, and Pneumocystis species in patients receiving blood or marrow transplantation. RZF has a favorable safety and tolerability profile and a low risk of drug-drug interactions. The pharmacokinetics of RZF allow for once-weekly dosing and broad distribution to lung and other target organs. • RZF was shown to prevent in vitro Pneumocystis biofilm formation and to reduce the viability of mature biofilms. 1 A previous prophylactic study was conducted using a broader range of RZF doses. In the current study, the efficacy of RZF was evaluated to better understand the minimum doses necessary to prevent Pneumocystis growth in a mouse model. INTRODUCTION METHODS • RZF demonstrated potent in vivo efficacy as prophylaxis against Pneumocystis in a mouse infection model at dose regimens much lower than the human equivalent Ph3 regimen of RZF 400 mg on week 1 followed by 200 mg once weekly. These data support the development of RZF for the prevention of invasive fungal infections including PCP. • Results in the present prophylactic study support the concept that the sexual cycle is obligate for Pneumocystis. Rezafungin inhibited 1,3-β-D-glucan synthesis, blocking sexual production and asci formation, resulting in prevention of infection. 1. Cushion MT, Collins MS. The effects of serum on the susceptibility of Pneumocystis carinii to the echinocandins in suspension and biofilm systems. Antimicrob Agents Chemother. 2011 Oct;55(10):4513-8. REFERENCES This study was supported by funding from Cidara Therapeutics, Inc. through the non-profit CERV. The work was performed at the Cincinnati VAMC. Rezafungin Prophylactic Efficacy in a Mouse Model of Pneumocystis Pneumonia B189 Group Drug Regimen Dose Schedule N 1 Control (steroid only) -- 10 2 Rezafungin 0.5 mg/kg 1x/wk IP 10 3 Rezafungin 0.5 mg/kg 2x/wk IP 10 4 Rezafungin 0.5 mg/kg qd IP 10 5 Rezafungin 5 mg/kg 1x/wk IP 10 6 Rezafungin 5 mg/kg 2x/wk IP 10 7 Rezafungin 5 mg/kg qd IP 10 8 Caspofungin 5 mg/kg qd IP 10 9 TMP/SMX 50/250 mg/kg 3x/wk 10 Colors of groups correspond to colors used in Figures 1 and 2. • C3H/HeN mice (N=10/group) were immunosuppressed (dexamethasone 4 mg/L in acidified drinking water) and infected intranasally with P. murina (2 x 10 6 nuclei/50 µL). Test agents were administered (Table 1), at the same time as inoculation to evaluate prophylactic efficacy. • After 6 weeks, mice were sacrificed and lung homogenates were processed for analysis to quantify nuclei (trophic) and asci forms (Fig 1). • Prophylaxis efficacy was based on reduction of organism burden compared with the control/steroid (C/S) group. Nuclei and asci counts were log transformed and analyzed by ANOVA; individual groups were compared by the Student Newman Keuls t test. Survival rates were compared using GraphPad Prism v5. Figure 1. Two-phase life cycle of Pneumocystis. In the pulmonary phase, proliferation of the fungi and transmissive agent of infection (asci) occur. In the extrapulmonary phase, asci become airborne and infect a new host. We previously showed that echinocandin treatment halts the sexual cycle by inhibiting 1,3-β-D-glucan synthesis, consequently blocking transmission as no asci are present. 2 Table 1. Test agents and dosing schedules by group DISCLOSURE Presenter Information: Taylor Sandison, MD, MPH | Cidara Therapeutics, Inc. | San Diego, CA 92121 USA | [email protected] Y-axis denotes limit of detection=4.2; colored columns represent study groups as shown in Table 1. Solid bracket denotes statistical significance (P value < 0.05) in difference between treatment groups and C/S. Dotted bracket denotes no statistical significant difference between treatment group and TMP/SMX. Figure 3. Survival curves after 42 days of treatment. RESULTS 2. Cushion MT, Linke MJ, Ashbaugh A, et al. Echinocandin treatment of Pneumocystis pneumonia in rodent models depletes cysts leaving trophic burdens that cannot transmit the infection. PLoS ONE 5(1): e8524 2010. • All RZF-treated mice had significantly reduced nuclei and asci burdens versus C/S, and all but the lowest dose of RZF (0.5 mg/kg 1x or 2x/wk) worked as well as TMP/SMX at reducing nuclei levels (Fig. 2). Similarly, all RZF-treated mice except the 0.5 mg/kg 1x/wk group showed reductions in asci comparable to that of TMP/SMX (Fig. 2). Survival rates (Fig. 3) were not statistically different between groups. Figure 2. Log 10 mean nuclei and asci counts after 6 weeks of treatment. Nuclei Counts Asci Counts CONCLUSIONS
Transcript of Mouse Model of Pneumocystis
www.ebmt.org #EBMT19
Melanie T. Cushion1,2,3, Taylor Sandison4, Alan Ashbaugh1,2.3
1University of Cincinnati, College of Medicine;
2Veterans Affairs Medical Center, Research Service;
3Cincinnati Education for Veterans Foundation, Cincinnati, OH;
4Cidara Therapeutics, San Diego, CA, USA
• Pneumocystis pneumonia (PCP) is an infection of the immunocompromised, and the risk of PCP warrants prophylaxis. Complications, such
as myelosuppression, nephrotoxicity, and intolerance associated with the current standard of care, trimethoprim-sulfamethoxazole,
(TMP/SMX) may hinder or interrupt prophylaxis.
• Rezafungin (RZF) is a novel echinocandin in development for prevention of invasive fungal disease caused by Candida, Aspergillus, and
Pneumocystis species in patients receiving blood or marrow transplantation. RZF has a favorable safety and tolerability profile and a low risk
of drug-drug interactions. The pharmacokinetics of RZF allow for once-weekly dosing and broad distribution to lung and other target organs.
• RZF was shown to prevent in vitro Pneumocystis biofilm formation and to reduce the viability of mature biofilms.1 A previous prophylactic
study was conducted using a broader range of RZF doses. In the current study, the efficacy of RZF was evaluated to better understand the
minimum doses necessary to prevent Pneumocystis growth in a mouse model.
INTRODUCTION
METHODS
• RZF demonstrated potent in vivo efficacy as prophylaxis against Pneumocystis in a mouse infection model at dose regimens much
lower than the human equivalent Ph3 regimen of RZF 400 mg on week 1 followed by 200 mg once weekly. These data support the
development of RZF for the prevention of invasive fungal infections including PCP.
• Results in the present prophylactic study support the concept that the sexual cycle is obligate for Pneumocystis. Rezafungin
inhibited 1,3-β-D-glucan synthesis, blocking sexual production and asci formation, resulting in prevention of infection.
1. Cushion MT, Collins MS. The effects of serum on the susceptibility of
Pneumocystis carinii to the echinocandins in suspension and biofilm systems.
Antimicrob Agents Chemother. 2011 Oct;55(10):4513-8.
REFERENCES
This study was supported by funding from Cidara Therapeutics, Inc. through the non-profit CERV. The work was performed at the Cincinnati VAMC.
Rezafungin Prophylactic Efficacy in a Mouse Model of Pneumocystis Pneumonia
B189
Group Drug Regimen Dose Schedule N1 Control (steroid only) -- 10
2 Rezafungin 0.5 mg/kg 1x/wk IP 10
3 Rezafungin 0.5 mg/kg 2x/wk IP 10
4 Rezafungin 0.5 mg/kg qd IP 10
5 Rezafungin 5 mg/kg 1x/wk IP 10
6 Rezafungin 5 mg/kg 2x/wk IP 10
7 Rezafungin 5 mg/kg qd IP 10
8 Caspofungin 5 mg/kg qd IP 10
9 TMP/SMX 50/250 mg/kg 3x/wk 10
Colors of groups correspond to colors used in Figures 1 and 2.
• C3H/HeN mice (N=10/group) were immunosuppressed (dexamethasone 4 mg/L in acidified drinking water) and infected intranasally with
P. murina (2 x 106
nuclei/50 µL). Test agents were administered (Table 1), at the same time as inoculation to evaluate prophylactic efficacy.
• After 6 weeks, mice were sacrificed and lung homogenates were processed for analysis to quantify nuclei (trophic) and asci forms (Fig 1).
• Prophylaxis efficacy was based on reduction of organism burden compared with the control/steroid (C/S) group. Nuclei and asci counts were
log transformed and analyzed by ANOVA; individual groups were compared by the Student Newman Keuls t test. Survival rates were
compared using GraphPad Prism v5.
Figure 1. Two-phase life cycle of Pneumocystis. In the pulmonary phase, proliferation of the fungi
and transmissive agent of infection (asci) occur.
In the extrapulmonary phase, asci become
airborne and infect a new host.
We previously showed that
echinocandin treatment
halts the sexual cycle by
inhibiting 1,3-β-D-glucan
synthesis, consequently
blocking transmission as
no asci are present.2
Table 1. Test agents and dosing schedules by group
DISCLOSURE
Presenter Information: Taylor Sandison, MD, MPH | Cidara Therapeutics, Inc. | San Diego, CA 92121 USA | [email protected]
Y-axis denotes limit of detection=4.2; colored columns represent study groups as
shown in Table 1. Solid bracket denotes statistical significance (P value < 0.05)
in difference between treatment groups and C/S. Dotted bracket denotes no
statistical significant difference between treatment group and TMP/SMX.
Figure 3. Survival curves after 42 days of treatment.
RESULTS
2. Cushion MT, Linke MJ, Ashbaugh A, et al. Echinocandin treatment of
Pneumocystis pneumonia in rodent models depletes cysts leaving trophic
burdens that cannot transmit the infection. PLoS ONE 5(1): e8524 2010.
• All RZF-treated mice had significantly reduced nuclei and asci
burdens versus C/S, and all but the lowest dose of RZF
(0.5 mg/kg 1x or 2x/wk) worked as well as TMP/SMX at
reducing nuclei levels (Fig. 2). Similarly, all RZF-treated mice
except the 0.5 mg/kg 1x/wk group showed reductions in asci
comparable to that of TMP/SMX (Fig. 2). Survival rates
(Fig. 3) were not statistically different between groups.
Figure 2. Log10 mean nuclei and asci counts after 6 weeks of treatment.Nuclei Counts Asci Counts
CONCLUSIONS
