# Presentation: 028824

## Microbiology

**Jeff Alder, Ph.D.**
**Vice President, Drug Discovery and Evaluation****Cubist Pharmaceuticals**

## Analysis of MIC Shifts

**Unprecedented microbiology database**
**1,215 *****S. aureus *****isolates were tested for MICs **
**First study to examine serial isolate susceptibility in SAB patients**
**MIC shifts to ******** 2 noted **
**Daptomycin- and vancomycin-treated patients **
**Different susceptibility criteria**
**Scientific investigations with these isolates**
**Bacteria, drug, patient**

## Wild-type Distribution of S. aureus Isolates Includes Daptomycin MICs of 2 μg/mL

|  | No. of
Isolates | MIC90
(μg/mL) | Range
(μg/mL) | MIC of 2 μg/mLn (%) |
| --- | --- | --- | --- | --- |
| Regional Surveys |  |  |  |  |
| 1998-2003 | 5,248 | 0.25 - 1 |  0.12 - 2 | 8 (0.15) |
| Global Surveillance Studies |  |  |  |  |
| 1999-2001 | 2,787 | 0.25 - 0.5 |  0.12 - 2 | 1 (0.04) |
| 	2002 | 2,623 | 0.5 |  0.12 - 2 | 2 (0.08) |
| 	2003 | 4,362 | 0.5 |  0.12 - 2 | 1 (0.02) |
| 	2004 | 5,260 | 0.5 |  0.12 - 2 | 2 (0.04) |
| 	2005 | 6,374 | 0.5 |  0.12 - 2 | 3 (0.05) |
| Total | 26,654 | NA |  0.12 - 2 | 17 (0.06) |

**MICs of 2 ****μ****g/mL were observed prior to approval (Sept ’03)**

## Daptomycin-treated Patients with Post-baseline Daptomycin MICs of 2 and 4 

**MIC 4 μg/mL (N**** ****=**** ****1)**
**1 failure (cRIE; large septic pulmonary emboli, tunnel infection)**
**MIC 2 μg/mL (N**** ****=**** ****6)**
**1 success (cBAC; vertebral osteomyelitis, debrided x2) **
**3 failures (cBAC; IV port infection, septic arthritis, ****retroperitoneal abscess)**
**2 failures (LIE; no valve replacement surgery) **
**Failed patients did not or could not receive adjunctive therapy (e.g., surgery, drainage)**

## Vancomycin-treated Patients with Post-baseline Vancomycin MICs of  2

**2 patients by Central Lab testing**
**1 success (cRIE)**
**1 failure (cBAC; septic thrombophlebitis)**
**5 additional patients by Local Lab testing**
**1 failure (LIE; no valve replacement surgery) **
**3 failures (cBAC; sternal osteomyelitis, abscesses, ulcers) **
**1 failure (uBAC; abdominal wound with mesh) **
**Failed patients did not or could not receive adjunctive therapy (e.g., surgery, drainage)**

## Serial Passage Experiments:Magnitude of MIC Shifts

- Serial Passage Experiments:Magnitude of MIC Shifts

**20**

**40**

**60**

**80**

**100**

**120**

**140**

**1**

**2**

**3**

**4**

**5**

**6**

**7**

**8**

**9**

**10**

**11**

**12**

**13**

**14**

**15**

**16**

**Day**

**Fold Change ****[(Strain MIC/Parent MIC)-1]**

**0**

## Genes Involved in S. aureus Susceptibility

| Genetic Change* | Isolate Source |  |  |  |  |
| --- | --- | --- | --- | --- | --- |
|  | Wild-type (Non-exposed) |  | SAB/SAIEStudy | Clinical Use | Serial Passage |
|  | (MIC  1) | (MIC 2) | (MIC 2-4) | (MIC 2-8) | (MIC 2-16) |
| mprF | - |  |  |  |  |
| yycG | - | - | - |  |  |
| rpoB | - | - | - | - |  |
| rpoC | - | - | - | - |  |

*******	****Genetic loci identified using whole genome comparisons between CA-MRSA MW2 ****	****and lab-derived MW2 strains with increasing daptomycin MICs**

***mprF***** mutations: ****	****Part of the wild-type distribution**
***yycG***** mutations: ****	****First unique change seen in MIC ******** 4 clinical ****	****isolates, but not seen in wild-type isolates**

## Genes Involved in S. aureus Susceptibility

*******	****Genetic loci identified using whole genome comparisons between CA-MRSA MW2 ****	****and lab-derived MW2 strains with increasing daptomycin MICs**

| Genetic Change* | Isolate Source |  |  |  |  |
| --- | --- | --- | --- | --- | --- |
|  | Wild-type (Non-exposed) |  | SAB/SAIE Study | Clinical Use | Serial Passage |
|  | (MIC  1) | (MIC 2) | (MIC 2-4) | (MIC 2-8) | (MIC 2-16) |
| mprF | - |  |  |  |  |
| yycG | - | - | - |  |  |
| rpoB | - | - | - | - |  |
| rpoC | - | - | - | - |  |

***mprF***** mutations: ****	****Part of the wild-type distribution**
***yycG***** mutations: ****	****First unique change seen in MIC ******** 4 clinical ****	****isolates, but not seen in wild-type isolates**

## Pharmacodynamics of S. aureus in MiceLab-derived Isolates of CA-MRSA MW2 

**1031**

**453**

**250**

**275**

- Pharmacodynamics of *S. aureus* in MiceLab-derived Isolates of CA-MRSA MW2

**Median AUC = 543 ****μg****·****hr/mL****with the human 6 mg/kg dose**

**MIC Value (****μg/mL****)**

**Total AUC for 3 log****10**** Reduction****(μg·hr/mL)**

**0**

**200**

**400**

**600**

**800**

**1000**

**1200**

**1400**

**1600**

**1800**

**2000**

**2**

**4**

**8**

**16**

**1**

**10**

**100**

**MICs ******** 2 respond to similar drug exposure (AUC)**
**MICs ******** 4 require increasing levels of drug exposure**

## Efficacy in Mice Against Baseline and Post-baseline Isolates from the SAB/SAIE Study

- Efficacy in Mice Against Baseline and Post-baseline Isolates from the SAB/SAIE Study

**152**

**212**

**105**

**037**

**183**

**136**

**172**

**Patient Number (Daptomycin-treated)**

**Total Plasma AUC for 3 log****10**** Reduction****(μg·hr/mL)**

**0**

**250**

**500**

**750**

**1000**

**1250**

**1500**

**Baseline**

**Post-baseline**

## Daptomycin Penetration into Simulated Endocardial Vegetations

**Daptomycin penetrates into rat fibrin clots; exerts bactericidal activity **

**Mortin *****et al*****. ASM 2003; Tsuji and Rybak. AAC 2005; Caron *****et al*****. AAC 1992.**

**T = 72h;**
**2 doses **

**T = 72h;**
**No treatment**

## Daptomycin Penetration into Simulated Endocardial Vegetations

**Daptomycin penetrates into rat fibrin clots; exerts bactericidal activity **
**Daptomycin achieved efficacy at simulated 6 mg/kg dose**

**Mortin *****et al*****. ASM 2003; Tsuji and Rybak. AAC 2005; Caron *****et al*****. AAC 1992.**

**T = 72h;**
**2 doses **

**T = 72h;**
**No treatment**

## Daptomycin Penetration into Simulated Endocardial Vegetations

**Daptomycin penetrates into rat fibrin clots; exerts bactericidal activity **
**Daptomycin achieved efficacy at simulated 6 mg/kg dose**
**14****C-daptomycin achieved homogenous penetration into ****rabbit vegetations**

**Mortin *****et al*****. ASM 2003; Tsuji and Rybak. AAC 2005; Caron *****et al*****. AAC 1992.**

**T = 72h;**
**2 doses **

**T = 72h;**
**No treatment**

## Global Surveillance Data (MRSA)

**Study Year**

**% Incidence**

**0**

**10**

**20**

**30**

**40**

**50**

**60**

**70**

**2000-2001**

**2002**

**2003**

**2004**

**2005**

****** ****0.12**

**0.25**

**0.5**

**1**

**2**

**MIC**

**Jones *****et al*****. Annual Surveillance Reports. 2002-2005.**

## Microbiology Summary

**Additional investigations due to failures at MIC ******** 2**
**Bacteria, drug, patient**
**No decisive bacterial or daptomycin factors **
**No trends in surveillance**
**Difficult to select for large MIC increases**
**Incremental genetic changes**
**Modeling shows adequate drug exposure and penetration **
**Patient-specific factors likely play a role**
**Complicated infections and outcomes**
**Adjunctive care important**
**Similar observations with vancomycin**