Voir ici :
<I>Pour l'essai à dose ascendante, 6 à 24 patients seront inscrits en cohortes de 3 patients par niveau de dose du zalutumumab. Le niveau de la dose pour chaque cohorte successive sera déterminé à l'aide de l'ensemble des données de sécurité observées dans les cohortes antérieures. Lorsque la dose maximale tolérée de zalutumumab sera établie, une cohorte supplémentaire de 12 patients sera formée et traitée à ce niveau.</I>
sur : http://www.caducee.net/breves/breve.asp?idb=7801&mots=all

Hmm, you'd think GSK would be familiar with the correct terminology.

http://www.gsk-clinicalstudyregister.com/protocol_detail.jsp...

This study is a Phase I single and repeat dose escalation study of GSK1265744 in healthy subjects and a single repeat dose cohort in HIV-1 infected subjects. The study is planned to consist of three parts. Part A will enroll two cohorts with a total of 18 subjects in a single dose escalation to evaluate safety, tolerability and PK. Part B plans to enroll three cohorts of 10 subjects to evaluate repeat doses of GSK126744 on safety, tolerability and PK. Part A and B will enroll healthy volunteers. Part C will enroll HIV-1 patients in a single cohort of 10 subjects. This cohort will evaluate the effects of repeat dose on safety, tolerability, PK and efficacy.

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Note added at 6 hrs (2010-12-06 16:40:09 GMT)
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http://www.fda.gov/downloads/Drugs/DevelopmentApprovalProces...

Study 1: The minimum number of patients by age group to be enrolled in the pharmacokinetic substudy in children ages 1 to 12 years with HSV or VZV infection is as follows:
Cohort 1: 1 year to < 2 years: 6 patients
Cohort 2: 2 years to < 6 years: 12 patients
Cohort 3: 6 years to < 12 years: 8 patients

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Note added at 6 hrs (2010-12-06 16:46:39 GMT)
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The minimum number being determined by the goals of the study (power, size of effect etc.) and not by the definition of "cohort".

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Note added at 11 hrs (2010-12-06 21:37:19 GMT)
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Example of an expansion cohort:

http://clinicaltrialsfeeds.org/clinical-trials/show/NCT01078...

Detailed Clinical Trial Description
- Since we are looking for the highest dose of the study drug that can be administered safely without severe or unmanageable side effects in participants that have melanoma, not everyone who participates will receive the same dose of the study drug. The dose participants will get will depend upon the number of participants who have been enrolled in the study before and how well they tolerated their doses. - Each treatment cycle lasts 28 days. Participants will take sorafenib orally twice a day and will receive bortezomib as an out-patient intravenous injection on Days 1, 8 and 15 of every cycle. - At the end of each treatment cycle, participants will be examined to determine whether their disease has worsened, improved or stayed the same, and to see if they are experiencing any side effects of treatment. The following tests will be done at these visits: physical examination, vital signs, blood tests and scans (repeated every 2 months). - Once the maximum tolerated dose of sorafenib and bortezomib have been determined, an additional 12 participants will be enrolled in this study. This is called the expansion cohort of this study. Participants enrolled in this cohort will be required to undergo a biopsy of the tumor lesion before they start study treatment and an additional biopsy after you start study treatment.