Clinical Pharmacology for Candin
Mechanism Of Action
Cellular hypersensitivity or delayed-type hypersensitivity (DTH) can be assessed by intracutaneous testing with bacterial, viral and fungal antigens to which most healthy persons are sensitized. A positive skin test denotes prior antigenic exposure, T-cell competency and an intact inflammatory response1,2. The reaction usually peaks between 24 and 48 hours after antigen is introduced into the skin and is manifest as induration at the test site.
Pharmacodynamics
The inflammatory response associated with the DTH reaction is characterized by an infiltration of lymphocytes and macrophages at the site of antigen deposition. Specific cell types that appear to play a major role in the DTH response include CD4+ and CD8+ T lymphocytes which leave the recirculating lymphocyte pool in response to exogenous antigen3. Both CD4+ and CD8+ lymphocytes have been recovered from DTH reactions elicited by Candida antigen4.
Clinical Studies
Response To CANDIN IN Healthy Adults
In one group of 18 subjects, 14 (78%) of the individuals reacted to CANDIN with an induration response of ≥ 5 mm at 48 hours. In a second study of 35 subjects, 21 (60%) had induration reactions ≥ 5 mm at 48 hours. In this study, 65% of males tested positive compared to 53% of females; the mean induration in responding males was 12.8 mm and in responding females was 13.0 mm.
Table 1: Response to CANDIN IN Healthy Adults8
| N | Age range (years) | Number reactions ≥ 5 mm at 48 hours | Response overall |
| Study 1 (a)* | 16 | 25-83 | 12 | |
| Male | | | | |
| Female | 2 | 61-69 | 2 | 78% |
| Study 2 Male | 20 | 23-63 | 13 | |
| Female | 15 | 28-62 | 8 | 60% |
| *(a) Control group in Table 2. |
Cellular Hypersensitivity Response To CANDIN In Adults With AIDS, Adults With HIV Infection (no- AIDS-indicator conditions) And Adult Control Subjects (Table 2)
Response to CANDIN in Adults with HIV Infection: In one study (Table 2), the skin test responses of adults with HIV infection were compared to those of healthy control subjects (age range AIDS 22 - 65, HIV positive 20 - 45, Controls 25 - 69). When HIV-infected subjects were classified by the CDC's 1993 revised classification system for HIV infection(5), a significant difference was found between AIDS patients and normal controls in both mean induration (p = 0.01) and proportion with ≥ 5 mm response (p > 0.01). The responses in HIV-infected patients (without AIDS-indicating conditions or AIDS-indicating CD4 T-cell counts) were less than in normal subjects, but the differences were not statistically significant.
In a second study involving 20 male patients (age range 26 - 57) diagnosed with AIDS based on clinical criteria only, one subject responded to CANDIN. In the same study 65% of the male control subjects had DTH reactions ≥ 5 mm to CANDIN (Table 1, Study 2). The mean induration response at 48 hours for control subjects was 8.33 mm compared to 1.78 mm for the AIDS subject. AIDS vs. control p-values were < 0.01 mean induration and < 0.01 induration ≥ 5 mm.
Because HIV infection can modify the DTH response to tuberculin, it is advisable to skin test HIV-infected patients at high risk of tuberculosis with antigens in addition to tuberculin (6). In a published study of DTH anergy, 479 subjects (334 males and 145 females) infected with HIV and being screened for tuberculosis were skin tested with several additional antigens, including CANDIN supplied under IND to the investigators. Only 12% reacted to tuberculin (≥ 5 mm), 57% reacted to CANDIN (≥ 3 mm) and 60% reacted to either tuberculin or CANDIN or both. In this study, a 3 mm induration response to CANDIN was considered positive. The authors concluded that in HIV-infected subjects, testing with other DTH antigens increases the accuracy of interpretation of negative tuberculin reactions.
Table 2: Cellular hypersensitivity response to CANDIN in adults with AIDS, adults with HIV infection (no-AIDS-indicator conditions) and adult control subjects
| Group | CD4 T-cell Count |
| Classification* | N | Zidov- udine Use | Range | Mean | Mean Indur- ation (mm) | N≥5 (mm) | % |
| AIDS | A3,B3,C | 32 | 14 | 4-483 | 145 | 3.35† | 9 | 28‡ |
| HIV POS. | A1,A2, B1,B2 | 28 | 13 | 201-1065 | 455 | 5.67 | 15 | 54 |
| Control | ---- | 18 | 0 | 554-1876 | 869 | 8.03 | 14 | 78 |
*(reference 12) † p=0.01 compared to Control. ‡ p<0.01 compared to Control. |
Cellular Hypersensitivity Response To CANDIN In Adults With Cancer (Table 3)
IIn one study of 18 patients with lung cancer, CANDIN elicited a positive induration response in five patients (28%). In a second series of 20 patients with metastatic cancer, no reactions ≥5 mm were observed (Table 3).
Table 3: Cellular hypersensitivity response to CANDIN in adults with cancer
| N | Age range | Number reactions ≥ 5 mm at 48 hours | Response |
| Study 1 | 18 | 52-75 | 5 | 28% |
| Study 2 | 20 | 47-81 | 0 | 0% |
REFERENCES
1. Middleton, E. Jr., Reed, C.E., Ellis, F.E., Adkinson, N.F., Jr., Yunginger, J.W., Busse, W.W., Allergy Principles and Practice, 4th Ed., Vol II, pp 963-982, Mosby, St. Louis, 1993.
2. Bernstein, I.L., ed., Proceedings of the task force of guidelines for standardizing old and new technologies used for the diagnosis and treatment of allergy, J. Allergy Clin. Immunol., 82: 487-526, 1988.
3. Paul, W.E., Fundamental Immunology, 3rd Ed., pp 75-76, Raven Press, New York, 1993.
4. MacPhee, M.J., Gordon, J., Christou, N.V., Sanchez-Cantu, L., Rode, H.H., Cells recovered from human DTH reactions: phenotypic and functional analysis. Cellular Immunology, 151: 80-96, 1993.