Subacute administration of a TRH analogue (RX77368) in motorneuron disease: an open study

Continuous response variable trial design in motor neuron disease: long term treatment with a TRH analogue (RX77368)

The continuous response variable controlled trial design is developed as a model for the efficient screening of candidate treatments in motor neuron disease. A TRH analogue (RX77368) and placebo were randomly allocated to 15 matched pairs of patients with motor neuron disease. With validated composite interval scores, this trial excluded a 50% or greater improvement with RX77368 at month 12 in scores of respiratory, lower limb, and activities of daily living function with greater than 90% power, and in bulbar function scores with 80% power. For upper limbs, 52% and 75% improvements were excluded at months 9 and 12 respectively with 80% power. Patients who died during the study had faster deterioration rates in bulbar and respiratory scores than their surviving pairs. The feasibility of screening drugs for significant biological effects with small sample sizes and good statistical power is shown. The difficulties of handling deaths and dropouts when using this design are discussed. Comparisons are made with sample sizes required using other scores and rating scales, as well as with those required in hazard and event rate studies. A simple clinical grading scale for motor neuron disease, with its corresponding composite interval scores, is described.

Accuracy, reproducibility and variability of quantitative assessments of bulbar and respiratory function in motor neurone disease

The validity of quantitative tests to assess bulbar and respiratory function used in therapeutic trials in motor neurone disease (MND) is studied in 26 MND and 21 age- and sex-matched control subjects. Five raters timed repeated visual and auditory stimuli generated by a metronome simulating bulbar tests. For all raters, mean error rate was 5.07%, correlation coefficient was 0.89 (and %difference of 1.53), and coefficient of variation (CV) was 3.18%. The experienced rater obtained significantly better %differences and CV. For all subjects and tests, mean correlation coefficient was 0.98, and mean CV was 8.8%. There were no significant differences in reproducibility or variability in readings obtained in MND and control subjects assessed by the experienced rater. The use of composite bulbar, but not respiratory, scores resulted in significant improvements in reproducibility and variability.

What do we really know about amyotrophic lateral sclerosis?

The cause of amyotrophic lateral sclerosis is unknown. In this review clinical and scientific data that are pertinent to understanding this disease are reviewed. There are currently several major controversies concerning the possible role of immunological factors, genetic factors, environmental toxins, and viral infection in pathogenesis. These concepts must be considered in relation to what is known about the disease in all its aspects, including epidemiological data, information on the classical and molecular pathology of the disease, and on associated involvement of other systems, e.g., the spinocerebellar pathways and frontal dementia. Only when all this information is assimilated can full understanding of the disease and, hopefully, a logical approach to treatment and prevention, be achieved.

Use of TRH analogues in motorneurone disease

TRH analogues have a longer half-life than does TRH and enhanced neuropharmacological actions. In motorneurone disease (MND), no benefit was reported with MK771 and DN1417. Focal, transient, and slight improvements in weakness and spasticity were described with CG3509. A controlled trial with a single intravenous dose of RX 77368 showed improvements in dysarthria, tongue movements, respiration, swallowing, and spasticity lasting up to 72 hours. Changes in muscle force were of no functional significance. There was an acute 25-30% increase in mean corrected fiber density and in mean macro-EMG parameters in biceps, but no change in amplitude or area of single macro-EMG motor units followed during the 2-hour infusions. An acute, direct or indirect, central effect of RX77368 on recruitment order or on activation threshold of pathological motor units is suggested. In a subacute open trial with repeated intravenous infusions of RX77368 (median 2 weeks), improvement in bulbar function in 8 of 12 responders, cramps (5 of 9), and spasticity (5 of 8) were maintained for medians of 18, 14, and 7 days, respectively. Side effects were prominent with doses above 0.2 mg/kg. Disease progression has not been halted with any analogue, but whether it may be usefully slowed down with RX77368 is worth investigating.