"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 )

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 days14 days21 days 0 ppm3 pens 110 ppm3 pens 220 ppm3 pens 330 ppm3 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 aa b b a,b different, p<.05

Summary Lesion Data % lobes % total lung 0 ppm ppm ppm ppm554.9

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 bb 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 rateReplications

% 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 K g/ da y a,b different, p<.05

Feed /Gain a,b different, p<.05 a ab bb

Lesions Scored Microscopically for Aging of MP Lesion AcuteSubacute regressing Chronic resolved Other Pneumonias earlylate 049 a 560a0a b ab c5c bc c0c c 6 a,b,c Means 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

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