# Presentation: 374747

## "Clinical Trials and Clinical Endpoints" 

- James R. Bradford, DVM, Dipl. ABVP
- Pharmacia Animal Health

## Mycoplasmal Pneumonia

- Clinical and production disease
- Recognized financial impact early ’70’s
- Research with Lincomycin began in 1974
- FDA approval “for the reduction in severity of pneumonia due to *Mycoplasma hyopneumoniae”* granted in 1978

## Mycoplasmal Pneumonia of Swine Is...

- A distinct clinical disease with distinct lesions and a recognized cause
- Often part of a more severe respiratory disease complex
- Potentiator  for *Pasteurella multocida*, some APP, PRRSV (Pijoan, Thacker)
- Additive with Swine Influenza Virus (Thacker and Halbur)
- Treatable as a single entity or as part of a complex

## Clinical Endpoints

- % of pigs affected
- Number of lobes involved in each pig
- % of lung involved
- Respiratory score
- Cough
- Respiratory difficulty

## Pivotal Studies

*In vitro* MIC determination for challenge strain correlated with concentration at site of infection
- Challenge trials - dose titration, duration of treatment
- Field efficacy trials – dose confirmation, fixed duration

## MIC Determination

*In vitro* MIC and susceptibility testing
- Strain 11
- MIC 0.2 μg/mL
- Pigs fed lincomycin at 110 ppm have a mean lung concentration of 0.6 μg/g (Range 0.40-0.71)

## Challenge Model

- Must have pigs free of *M. hyopneumoniae*
- Usually very mild disease compared to field challenge
- All animals at same stage of infection
- Can treat at earliest appearance of clinical signs
- May give false sense of efficacy

## Challenge Trial – Materials and Methods

- Single barn
*M. hyopneumoniae-*free pigs 4-6 weeks of age
- Randomly allotted to treatments based on sex, weight, and age
- Challenged pigs and unchallenged controls housed in same barn in separate air spaces (confirmation of negative status)

## Challenge Method

- All pigs in challenged groups
- Challenged 2 consecutive days
- 2 doses each day (intranasal and intratracheal)
- Fresh lung homogenate in Eagle’s medium
- Non-challenged controls were inoculated with Eagle’s medium

## Treatments – Challenged Pigs

|                    Duration

Inclusion rate | 7 days  | 14 days | 21 days |
| --- | --- | --- | --- |
| 0 ppm |  |  | 3 pens |
| 110 ppm | 3 pens | 3 pens | 3 pens |
| 220 ppm | 3 pens | 3 pens | 3 pens |
| 330 ppm | 3 pens | 3 pens  | 3 pens |

## Unchallenged Pigs

- Separated by solid partitions
- Confirm that *M. hyo* challenge caused the lung lesions
- 4 pens –
- 3 non-medicated  - validate *M. hyo* status
- one medicated – demonstrate swine dysentery control or growth effect was not responsible for performance benefits

## Treatment Initiation 

- At onset of clinical signs (Clinical disease present)
- Expected to be day 10 PI
- Actually day 8 PI – 13.6% of pigs coughing

## Clinical Endpoints

- % of lobes with lesions – incidence measure
- % of total lung with lesions – severity measure

## Lesions Observed

- a

- a

- b

- b

- a

- a

-  b

- b

- a,b different, p<.05

## Summary Lesion Data

|  | % lobes | % total lung  |
| --- | --- | --- |
| 0 ppm | 74.6 | 11.6 |
| 110 ppm | 75 | 12.4 |
| 220 ppm | 46 | 4.4 |
| 300 ppm | 55 | 4.9 |

## Duration of Treatment% Lobes with Lesions-Pooled Data

## Duration of Treatment% Lung Involved-Pooled Data

## Duration of Treatment% Lobes with Lesions

## Duration of Treatment% Lung with Lesions

## Performance Parameters

- a

- a

- b

- b

- a

- a

- b

- b

- a,b different, p<.05

## Conclusion

- In the challenge model, lincomycin at 220 and 330 ppm resulted in a significant reduction in severity and incidence of lesions caused by *M. hyopneumoniae*.
- The optimum treatment regime based on lesion and performance data was 220 ppm for 21 days.

## Field Trials

- Herds with history of problems with MPS
- Pigs at an age already likely infected with MPS

## 4 Field Trials

- Indiana, Florida, Alabama, and Minnesota
- Pigs 8-12 weeks of age
- 6 cohort pigs killed and necropsied to confirm disease
- 3 sites tested 4 inclusion rates: 0,110, 220, 330 ppm
-  1 site tested 0, 220 ppm only

## Clinical Observations

- Gross Pathology
- Number of lobes involved
- Estimated percent of total lung involved
- Microscopic Pathology
- Right cardiac lobe sampled based on lesion location for histopathologic scoring
- Production Parameters (ADG and ADFI)

## Results

- Data from all 4 sites was pooled, making the necessary statistical adjustments to compensate for unequal numbers of replications, pens and pigs at each site.

## Replications per Treatment

| Inclusion rate | Replications |
| --- | --- |
| 0 | 15 |
| 110 | 12 |
| 220 | 15 |
| 330 | 12 |

## % Pigs with MPS Lesions

- An estimate of the number of pigs exposed for sufficient time to develop lesions

## % Lobes Affected –All Pigs

- Lincomycin suppressed the advancement of the disease process.

- %

- a

- ab

- b

- b

- a,b different, p<.05

## % Lobes Affected – Pigs With Lesions

- Lesions may or may not have been present prior to treatment.

- %

## Mean % Total Lung Involved All Pigs

- 220 ppm reduced severity by 49%, 110 ppm by 27%(ns)

- a

- ab

- b

- b

- a,b different, p<.10

- %

## Mean % Total Lung Involved Pigs With Lesions

- %

## ADG  (kg)– Least square Means

- a

- b

- b

- b

- Kg/day

- a,b different, p<.05

## Feed /Gain

- a,b different, p<.05

- a

- ab

- b

- b

## Lesions Scored Microscopically for Aging of MP Lesion

|  | Acute |  | Subacute 
regressing | Chronic 
resolved | Other 
Pneumonias |
| --- | --- | --- | --- | --- | --- |
|  | early | late |  |  |  |
| 0 | 49a | 5 | 6 | 0a | 10 |
| 110 | 22b | 19 | 17 | 14ab | 6 |
| 220 | 5c | 8 | 12 | 29bc | 12 |
| 330 | 0c | 4 | 22 | 38c | 6 |

- a,b,cMeans in the same column with different superscripts differ significantly (p<.05)

**% of Pigs**

## Trial Conclusion

- Lincomycin administered in the feed at 220 ppm for 21 days is effective in the reduction of pneumonia lesions associated with *Mycoplasma hyopneumoniae.*

## Conclusions Based on 25 Years Experience

- It is possible to measure clinical endpoints  of mycoplasmal pneumonia both in clinical trials  and in field trials.
- The approval process to provide substantial proof of efficacy was was rigorous and has stood the test of time.
- Production parameters are an important auxiliary component of the research process, but not the approval process.

## If We Designed a Plan Today.....

- Similar approach
- Laboratory – *in vitro* determination of efficacy correlated with drug at the site of infection
- Challenge – validated challenge models run in production-like facilities for dose and duration selection
- Field trials – field efficacy trials with dose and duration confirmation

## Slide 38

## If We Designed a Plan Today.....

- Field efficacy trials –
- Multi-location – production units
- History of respiratory disease with *M.* *hyopneumoniae* as a key component
- Co-infections with PRRSv acceptable/welcome
- Experimental unit ? – pen, room, barn, site

## If We Designed a Plan Today.....

- Clinical Endpoints
- % lung involved and % pigs affected would still be critical measurements
- % lung involved could be measured more accurately today with grids and computer calculation and could be measured on a sample of pigs killed over the course of the trial
- Fluorescent antibody test would provide better confirmation of cause of pneumonia

## Lincomix effects on culling

- Pharmacia - Bradford  9/00

## Lincomix pulled

## Lincomix pulled

## Lincomix pulled