Antitumor effects of an antibody-carboxypeptidase g2 conjugate in combination with a benzoic acid mustard prodrug

The F(ab’)₂ fragment of the antitumor monoclonal antibody, A5B7, was covalently linked to the bacterial enzyme carboxypeptidase G2 (CPG2). The resulting conjugate was used in combination with a prodrug of a benzoic acid mustard alkylating agent to treat human colon tumor xenografts in a two-step targeting strategy, antibody-directed enzyme produrug therapy (ADEPT). The prodrug, 4-[(2-chloroethyl) (2-mesyloxyethyl) amino]-benzoyl-l-glutamic acid is rapidly converted by CPG2 to a drug that is at least 15x more toxic in vitro against LS174T colorectal tumor cells than the prodrug. Optimal tumor/ blood ratios of the A5B7-CPG2 were achieved 72 h after administration of the conjugate to athymic mice bearing established LS174T tumor xenografts. Significant antitumor activity was seen in LS174T tumor-bearing mice treated with the conjugate followed 3 d later by the prodrug. In contrast, prodrug, conjugate, or active drug alone did not result in any antitumor activity in this tumor model. These studies demonstrate the advantage of a two-step ADEPT system for the treatment of colorectal cancer.     

Choriocarcinoma after Hydatidiform Mole. Studies Related to Effectiveness of Follow-up Practice after Hydatidiform Mole

Chemotherapy, in conjunction with other methods of treatment, was used in 100 patients with invasive hydatidiform mole or choriocarcinoma following mole. When treatment was instituted within two to six months of the antecedent mole serious drug resistance was not encountered, drug toxicity was slight, the duration of treatment was comparatively short, and sustained remissions were obtained in 57 out of 60 patients. When the start of chemotherapy was delayed beyond six months drug resistance occurred in many instances, toxicity was often severe, the duration of treatment was much longer, and sustained remissions were obtained in 22 out of 40 patients.The practice of giving prophylactic chemotherapy to all patients with mole is not established as effective or safe. Differences in the social background to hydatidiform mole in different geographical areas may be such that conclusions based on evidence from one area are not necessarily applicable to another.Careful follow-up after mole remains essential, though present methods often fail to ensure recognition of choriocarcinoma while it is still curable. Standard qualitative and quantitative methods for detecting the continued excretion of chorionic gonadotrophin, though useful, are sometimes too insensitive. It is suggested that to supplement local arrangements some form of centralized or regionalized follow-up service based on notification of patients with hydatidiform mole, and making use of radioimmunoassays for chorionic gonadotrophin, could reduce deaths attributable to late diagnosis.     

Computer system for assisting with clinical interpretation of tumour marker data.

OBJECTIVE--To design and evaluate a computer advisory system for the treatment of gestational trophoblastic tumour. DESIGN--A comparison of clinicians'' treatment decisions with those of the computer system. Two datasets were used: one to calibrate the system and one to independently evaluate it. SETTING--Department of medical oncology. PATIENTS--Computerised records of 290 patients with low risk gestational trophoblastic tumour for whom the advisory system could predict the adequacy of treatment. The calibration set comprised patients admitted during 1979-86(227) and the test set patients during 1986-89(63). MAIN OUTCOME MEASURES--The system''s accuracy in predicting need to change treatment compared with clinicians'' actions. The mean time faster that the system was in predicting the need to change treatment. RESULTS--On the calibration dataset the system was 94% (164/174) accurate in predicting patients whose treatment was adequate, recommending change when none occurred in only 10 (6%) patients. In patients whose treatment was changed the system recommended change earlier than clinicians in 39/53 cases (74%), with a mean time advantage of 14.9 (SE 2.02) days. On the test dataset the system had an accuracy of 91% (31/34) in predicting treatment adequacy and a false positive rate of 9% (3/34). The system recommended change earlier than clinicians in 22/29 cases (76%), with a mean time advantage of 12.5 (2.22) days. CONCLUSIONS--The computer advisory system could improve patient management by reducing the time spent receiving ineffective treatment. This has implications for both patient time and clinical costs.