F1-840
Synthesis, Structure and In Vitro Activity of the Neoglycoside ACHN-490
J. B. AGGEN, A. A. GOLDBLUM, P. DOZZO, M. S. LINSELL, M. J. GLIEDT, D. J. HILDEBRANDT, E. S.
ARMSTRONG, S. LOPEZ, M. GOMEZ, G. H. MILLER, K. B. WLASICHUK, R. DIOKNO, H. E. MOSER;
Achaogen,
South San Francisco, CA.
Background: The rapid emergence of drug resistance in Gram-negative bacteria is causing alarm in hospitals and health care facilities
around the world. With few new agents in the pipeline to address this growing threat, new antibiotics effective against drug resistant (R)
strains of Gram-negative bacteria are desperately needed. A focused medicinal chemistry campaign identified the neoglycoside, a nextgeneration aminoglycoside, ACHN-490 as a potentially useful agent. ACHN-490 is a broad-spectrum, rapidly bactericidal agent with
excellent potency against Gram-negative and select Gram-positive bacteria. Unlike other aminoglycosides (AGs), ACHN-490 retains
effectiveness against widespread and increasing resistance from AG-modifying enzymes (AMEs). Methods: ACHN-490 was synthesized in
8 steps from sisomicin. ACHN-490 was tested for antibacterial activity using the CLSI microbroth dilution method against a panel of 26
organisms with characterized AG resistance mechanisms (AGRM). Activity was confirmed against a broader panel of 461 Gram-negative
and Gram-positive clinical isolates. The AG-R organisms in this collection were selected to represent the most clinically relevant AGRM.
AMEs in the collection were confirmed by colony PCR. Results: The MIC s of ACHN-490 against AG-R Enterobacteriaceae were all ≤4
90
μg/mL with the exception of P. mirabilis and indole positive Proteae (MIC s 8 and 16 μg/mL respectively). The MIC
90
90
of ACHN-490
against AG-R staphylococci was 2 μg/mL. ACHN-490 was less active against AG-R P. aeruginosa and A. baumannii with changes in
permeability/efflux. Conclusion: ACHN-490 has emerged as a promising new antibacterial agent with potential to rejuvenate the AG
class of antibiotics, and thus has been advanced into early clinical development.
F1-841
The Bactericidal Activity of the Neoglycoside ACHN-490 against Aminoglycoside-Resistant Bacteria
1
1
1
1
1
G. E. ZURENKO , D. A. STAPERT , M. L. KNECHTEL , N. NICHOLS , D. L. SHINABARGER , E. S. ARMSTRONG
2
2
2
2
2
2
1
, J. B. AGGEN , L. A. FEENEY , A. KUBO , R. D. MATIAS , G. H. MILLER ;
Micromyx, Kalamazoo, MI,
2
Achaogen, South San Francisco, CA.
Background: ACHN-490 is a neoglycoside, a next-generation aminoglycoside (AG), in early clinical development. We assessed the
bactericidal properties of ACHN-490 and comparator agents against 1 reference strain and 7 clinical isolates of Gram-positive and negative bacteria known to produce different aminoglycoside-modifying enzymes (AMEs) such as acetyltransferases (AAC),
phosphotransferases (APH), and nucleotidyltransferases (ANT). Methods: MIC values were determined using a broth microdilution
method described by CLSI. Time kill assays were conducted using drug concentrations of 2-, 4-, 8-, 16-, and 32-fold the MIC. Inoculated
vessels were sampled at 1, 2, 4 and 24 h for determination of viable count, and the log CFU/mL was determined and plotted vs. time. A
10
bactericidal effect was defined as a ≥ 3 log
10
CFU/mL decrease relative to the initial count. Results: MIC data showed that ACHN-490
inhibited all test strains at ≤2 µg/mL, regardless of the presence of AMEs. In time kill studies, the agent demonstrated extremely rapid
bactericidal activity against all organisms. ACHN-490 produced a bactericidal effect between 1 and 4 h for all strains. For most strains,
this was observed at all test concentrations; S. aureus [APH(2’)-I+AAC(6’)-I] required ACHN-490 concentrations >4x MIC to achieve a
>3-log decrease. Most of the strains demonstrated re-growth at 24 h at 2x the MIC in the presence of either ACHN-490 or the
comparator. There was evidence of re-growth at 24 h for E. coli [AAC(3)-IV], E. coli [AAC(6’)-I], and E. aerogenes [AAC(6’)-I] at ≤ 4x
the MIC, but not at ≥ 8x the MIC. Conclusions: ACHN-490 demonstrated a potent, rapid, bactericidal effect for strains harboring known
resistance mechanisms to widely-used aminoglycosides. The stability of ACHN-490 to common AMEs and the bactericidal properties of the
agent support its continued development.
F1-842
Activity of ACHN-490, a Novel Neoglycoside Antibiotic, against Contemporary Gram-Negative Clinical Isolates from
Brooklyn, NY Hospitals
C. GEORGESCU, D. MARTIN, S. BRATU, J. QUALE, D. LANDMAN;
State Univ. of New York Downstate Med.
Ctr., Brooklyn, NY.
Background: MDR Gram-negatives are a growing problem. We evaluated the activity of ACHN-490, a novel neoglycoside antibiotic,
against a collection of contemporary Gram-negatives. Methods: Unique patient isolates of P. aeruginosa (PA), A. baumannii (AB), K.
pneumoniae (KP), E. coli (EC), and Enterobacter spp. (EB) from prior surveillance studies at 16 Brooklyn, NY hospitals were selected
based on resistance patterns. Most isolates were fingerprinted by automated ribotyping. MICs were performed by broth microdilution.
PCR was used to identify genes for aminoglycoside-modifying enzymes (AMEs) in AB and KP and KPC in Enterobacteriaceae (EN). The
expression of the efflux genes mexA, mexC, mexE and mexX in PA, and adeB in AB was assessed by real-time RT-PCR. Results: 204
isolates were tested. Ribotyping revealed that 55% of isolates were unique strains. 44% of the PA and AB isolates were carbapenemresistant, and 18% of the EN were KPC+. Susceptibility testing (Table) revealed that ACHN-490 had comparable activity to amikacin
against PA and AB, and excellent activity against KP, EC, and EB, including amikacin-resistant and KPC+ strains. Among AB, isolates with
aacA4 were more likely to have ACHN-490 MICs > 4 (93% vs. 50%, P=0.01); however, some isolates without AMEs achieved MICs > 16.
Among AB, isolates with increased expression of adeB were more likely to have ACHN-490 MICs > 8 (69% vs. 13%, P<0.001). No
relation was found between the presence of AMEs and ACHN-490 activity in KP isolates. Among PA, no relation was found between ACHN490 activity and efflux gene expression.
PA (n=33)
AB (n=38)
KP (n=71)
MIC50
MIC90
Susceptible
ACHN-490
8
16
Amikacin
4
16
94%
Gentamicin
4
64
67%
Imipenem
4
>8
55%
ACHN-490
8
>16
Amikacin
8
64
82%
Gentamicin
16
>64
24%
Imipenem
4
>8
55%
ACHN-490
0.5
1
Amikacin
16
64
58%
EC (n=32)
EB (n=30)
Amikacin-Resistant-EN (n=35)
Gentamicin
1
>64
59%
Imipenem
0.25
>8
79%
ACHN-490
1
2
Amikacin
4
16
91%
Gentamicin
1
64
72%
Imipenem
0.125
4
91%
ACHN-490
1
4
Amikacin
4
16
93%
Gentamicin
1
>64
70%
Imipenem
0.5
2
93%
ACHN-490
0.5
2
KPC+-EN (n=24)
ACHN-490
0.5
4
Conclusions: ACHN-490 shows promise as a novel agent against EN, including MDR-KPC+ strains.
F1-843
Activity of ACHN-490, a Novel Neoglycoside Antibiotic, against Complicated Urinary Tract Infection (cUTI) Pathogens From
the United States (USA) and Europe (EU)
1
1
2
2
2
1
D. BIEDENBACH , R. N. JONES , E. S. ARMSTRONG , J. B. AGGEN , G. H. MILLER ;
JMI Lab., North
2
Liberty, IA, Achaogen Inc, S San Francisco, CA.
Background: This study determined the activity of ACHN-490 against species that commonly cause cUTIs worldwide. Methods: Isolates
were collected from 47 medical centers in the USA and EU (10 countries) from urine or blood culture with the source of bacteremia
documented as a UTI. Strains were susceptibility (S) tested against ACHN-490, gentamicin (GEN), amikacin (AMK) and 10 comparators
by CLSI broth microdilution. Pathogens (no. 169) included: E. coli (EC), Klebsiella spp. (KSP), Enterobacter spp. (EBS), Citrobacter spp.
(CBS), P. mirabilis (PM), M. morganii (MM), P. aeruginosa (PSA), S. aureus (SA) and S. saprophyticus (SSAP). Results: MIC values for
90
ACHN-490 ranged from 0.5 to 2 µg/ml among EC, KSP, EBS and CBS. Higher MIC
90
values were observed for PM and MM (4 - 8 µg/ml),
the highest was PSA (MIC , 16 µg/ml). ACHN-490 was very active against SSAP with MIC
90
including 43.5% oxacillin-resistant (R) strains, had a MIC
90
50/90
values of ≤0.25/0.5 µg/ml. SA isolates,
of 2 µg/ml. Overall S rates to GEN and AMK were 86.4 and 94.1%,
respectively; and ACHN-490 inhibited 90.5 and 98.8% of strains at ≤4 and ≤16 µg/ml, respectively. Staphylococcal S rates to
ciprofloxacin (CIP), pip/tazo (P/T), nitrofurantoin and trim/sulfa (T/S) were 61.9, 73.8, 33.3 and 100%, respectively. S rates for CIP, P/T
and T/S against enteric pathogens were 77.8, 88.0 and 68.5%, respectively. PSA isolates were only 52.6% S to CIP and 73.7% S to P/T.
Conclusions: ACHN-490 was active against Gram-negative pathogens, SA and SSAP that are the leading causes of cUTIs, even in the
presence of mechanisms that caused R to current front-line antimicrobial agents.
Cumulative % inhibited at ACHN-490 MIC (µg/ml)
Organism/phenotype(no. Tested)
≤0.25
0.5
1
2
4
8
16
32
E. coli (21)
0.0
19.0
61.9
100.0
-
-
-
-
Klebsiella spp. (21)
19.0
95.2
100.0
-
-
-
-
-
Enterobacter spp. (16)
0.0
75.0
100.0
-
-
-
-
-
Citrobacter spp. (15)
0.0
73.3
86.7
93.3
100.0
-
-
-
P. mirabilis (20)
0.0
0.0
5.0
45.0
90.0
95.0
100.0
-
M. morganii (15)
0.0
0.0
6.7
60.0
86.7
100.0
-
-
P. aeruginosa (19)
0.0
0.0
0.0
0.0
36.8
73.7
89.5
100.0
S. aureus (23)
0.0
13.0
60.9
95.7
100.0
-
-
-
S. saprophyticus (19)
89.5
94.7
100.0
-
-
-
-
-
F1-844
Activity of ACHN-490 in Combination with Daptomycin, Ceftobiprole, or Linezolid against 25 Methicillin-Resistant
Staphylococcus aureus by Synergy Time-Kill
G. LIN, L. M. EDNIE, P. C. APPELBAUM;
Hershey Med. Ctr., Hershey, PA.
Background: Combination of new drugs with existing agents represents a promising avenue for treatment of multidrug-resistant S.
aureus. ACHN-490 is a neoglycoside currently in clinical development that was tested alone and in combination with daptomycin (DAP),
ceftobiprole (BPR)(synthesized by Achaogen), and linezolid (LZD) against MRSA by synergy time-kill method. Methods: The 25 isolates
tested included 2 hVISA, 2 VISA, and 5 VRSA, 10 hospital-acquired and 6 community-acquired methicillin-resistant S.aureus (MRSA)
strains. MICs were by broth macrodilution and potency of each of the 4 drugs alone was determined via time-kill methodology. For
synergy time-kills the concentration of each drug was chosen from the MIC result so that 1 drug demonstrated minimal activity while the
other was more active. Synergy was defined as ≥2log
10
decrease in CFU/mL between the combination and its more active component at
3, 6, 12, and 24 h. Results: MICs (µg/ml) of drugs alone were: ACHN-490, 0.5-8; daptomycin, 0.25-4; ceftobiprole, 0.5-2 and linezolid,
2-4. Synergy results were:
3h
6h
12 h
No. strains showing synergy
Range (µg/ml)
No. strains showingsynergy
Range (µg/ml)
No. strains
ACHN-490/ DAP
15
0.12-2/0.12-0.25
14
0.25-2/0.12-2
21
ACHN-490/ BPR
1
1/0.25
2
1-4/0.5
7
ACHN-490/ LZD
0
0
1
Combination of ACHN-490 + daptomycin yielded the highest rate of synergy at the various time points at subMIC levels, with 15 strains
showing synergy at 3 h, 14 strains at 6 h, 21 strains at 12 h, and 22 strains showing synergy at 24 h. ACHN-490 + ceftobiprole yielded
synergy in 1 strain after 3 h, 2 strains at 6 h, 7 strains at 12 h, and 9 strains at 24 h. ACHN-490 + linezolid yielded only 1 strain with
synergy at 12 h and 3 strains at 24 h. Conclusions: Combination of subinhibitory concentrations of ACHN-490 + daptomycin yielded
significant synergy, even in the 2 VISA strains which were initially daptomycin non-susceptible.
F1-845
In Vivo Efficacy of the Neoglycoside ACHN-490 against Enterobacteriaceae and MRSA
N. REYES, J. AGGEN, C. KOSTRUB;
Achaogen, Inc, South San Francisco, CA.
Background: ACHN-490 is a novel neoglycoside, a next-generation aminoglycoside (AG), in clinical development. ACHN-490 shows
broad-spectrum bactericidal activity in vitro, and its potency is unaffected by most types of aminoglycoside-modifying enzymes (AMEs)
that confer resistance to AGs. Methods: The in vivo activity of ACHN-490 in the mouse neutropenic thigh model was measured against 8
strains: susceptible strains of E. coli and Klebsiella pneumoniae; two multi drug resistant (MDR) clinical isolates of E. coli and K.
pneumoniae that display resistance to multiple drug classes (including AGs); methicillin-resistant S. aureus (ATCC 33591); and two
Klebsiella-producing carbapenemase (KPC)-expressing strains (Klebsiella and Serratia). For this efficacy model, CD-1 mice were rendered
neutropenic by 2 injections of cyclophosphamide, and inoculated intramuscularly with a known number of colony forming units (CFU) of
bacteria. Antibiotic was administered by SC injection, 2 and 14 hours after bacterial challenge. At 26 hours, infected thigh tissue was
harvested, homogenized, and plated to count CFUs. Untreated control animals were harvested at 2 hours post-infection to assess the
initial bacterial load. Results: ACHN 490 performed well against all 8 strains, reducing bacterial titers below the initial bacterial load
(static level) in each case. The ratio of in vivo efficacy to in vitro potency (ED50/MIC) of ACHN-490 was comparable to gentamicin,
demonstrating that ACHN-490 maintains the favorable PK/PD profile of currently marketed AGs. Conclusions: These results provide in
vivo confirmation of the in vitro activity of ACHN 490 against strains of Gram-negative bacteria, including those expressing multiple
resistance mechanisms. These studies also demonstrate the in vivo efficacy of ACHN-490 against MRSA.
F1-846
Pharmacokinetics of the Neoglycoside ACHN-490 in Mouse, Rat and Dog
R. T. CASS, J. V. MCKINNELL, B. XIE, D. E. KARR, D. E. SCHMIDT JR;
Achaogen, Inc., South San Francisco,
CA.
Background: ACHN-490 is a neoglycoside, a next-generation aminoglycoside (AG), in clinical development. In vitro and in vivo models
have demonstrated that AG bactericidal activity is concentration-dependent; higher concentrations of free drug cause faster killing of
exposed bacteria. The ratios of peak serum concentration (C ) to the minimum inhibitory concentration (MIC) of the target pathogen
max
(C
max
/MIC) and area under the time-concentration curve (AUC) to the MIC (AUC/MIC) are important indicators of the bactericidal activity
of AGs. As such, the pharmacokinetic (PK) profile, and particularly these ratios, are important pharmacodynamic (PD) parameters that
predict AG efficacy. Methods: Male CD-1 mice, Sprague Dawley rats and beagle dogs were administered ACHN-490 intravenously. Blood,
urine and kidney samples were taken over 24 hours and analyzed for ACHN-490 levels using LC-MS/MS. PK parameters were determined
by noncompartmental analysis using WinNonLin. Plasma protein binding was determined using equilibrium dialysis. In vitro stability was
determined using commercially available plasma, microsomes and hepatocytes. Results: The PK profile of ACHN-490 after intravenous
dosing was similar in mice, rats, and dogs. In rats, C
and exposure (AUC) were dose-linear to 75 mg/kg. ACHN-490 was renally
max
cleared rapidly in both rats and dogs (t
1/2
~1 hr). ACHN-490 distributed to rat kidneys. The volume of distribution closely matched
extracellular fluid volumes. ACHN-490 had low plasma protein binding (<20%). ACHN-490 was stable when exposed to plasma, liver
microsomes and hepatocytes and did not inhibit the 5 major human CYPs in vitro. Conclusions: ACHN-490 is metabolically stable and
unlikely to show drug-drug interactions. The short elimination half-life of ACHN-490 observed in preclinical species predicts a short halflife in humans (~1 hr). The PK profile of ACHN-490 supports use of high doses in short infusions, administered once-daily to achieve high
C
and AUC, which are important for efficacy and safety.
max