Improved pharmacokinetic properties of a polyethylene glycol-modified form of interferon-beta-1a with preserved in vitro bioactivity.

Interferon therapies suffer from a relatively short half-life of the products in circulation. To address this issue we investigated the effects of polyethylene glycol modification (PEGylation) on the pharmacokinetic properties of human interferon (IFN)-beta-1a. PEGylation with a linear 20-kDa PEG targeted at a single site on the N-terminal amine had no deleterious effect on its specific activity in an in vitro antiviral assay. In monkeys, PEG IFN-beta-1a treatment induced neopterin and beta2-microglobulin expression (pharmacodynamic markers of activity). Systemic clearance values in monkeys, rats, and mice decreased, respectively, from 232, 261, and 247 ml/h/kg for the unmodified IFN-beta-1a to 30.5, 19.2, and 18.7 ml/h/kg for the PEGylated form, while volume of distribution values decreased from 427, 280, and 328 ml/kg to 284, 173, and 150 ml/kg. The decreased clearance and volume of distribution resulted in higher serum antiviral activity in the PEG IFN-beta-1a-treated animals. In the rat, a more extensive set of dosing routes was investigated, including intraperitoneal, intratracheal, and oral administration. Bioavailability for the PEG IFN-beta-1a was similar to the unmodified protein for each of the extravascular routes examined. For the intraperitoneal route, bioavailability was almost 100%, whereas for the oral and intratracheal routes absorption was low (<5%). In rats, subcutaneous bioavailability was moderate (28%), whereas in monkeys it was approximately 100%. In all instances an improved pharmacokinetic profile for the PEGylated IFN-beta-1a was observed. These findings demonstrate that PEGylation greatly alters the pharmacokinetic properties of IFN-beta-1a, resulting in an increase in systemic exposure following diverse routes of administration.

Response of human lung tumor xenografts to treatment with a somatostatin analogue (Somatuline).

Four human small cell lung carcinomas, NCI-H69, NCI-N417, NCI-H345, LX-1, and a non-small cell lung carcinoma, H-165, implanted s.c. as tumor xenografts in athymic nude mice, were treated with Somatuline (BIM-23014C), an endocrinologically potent octapeptide analogue of somatostatin. All tumors responded, although in varying degrees, with percentage of test/control values ranging from 3 to 88. Somatuline administered as a perilesional infusion effectively inhibited xenograft growth inducing prolonged remissions. When treatment was terminated, some tumors regrew, suggesting antimitogenic activity rather than cytocidal. Absence of observable systemic or local toxicity during prolonged treatment would support this conclusion and suggest the feasibility of long term maintenance therapy with a resultant extended survival.

Activity of two phase I drugs N-methylformamide (NSC-3051) and Echinomycin (NSC-526417) against fresh surgical explants of human tumors in the 6-day subrenal capsule (SRC) assay.

The potential clinical activity of the new phase I drugs N-methylformamide (N-MF) and Echinomycin (ECH) was examined while still undergoing clinical toxicology trials by testing against fresh surgical explants of human tumors in the 6-day in vivo SRC Assay. Sixty-nine tumors representing different histologic types including breast, lung, colon, ovarian, and cervical, as well as neoplasms of undiagnosed origin, were screened against N-MF (NSC-3051) and ECH (NSC-526417) simultaneously with five standard chemotherapeutic agents used clinically for treatment of the specific type of cancer. Thus, activity of N-MF and ECH could be compared directly with that of standard agents tested in the same assay. Treatment schedule was QD1-5, and the criterion for drug activity was tumor graft regression greater than 20%. N-MF was active against 15/69 tumors with a response rate of 22%. ECH was also active against 15/69 tumors, yielding the same response rate. Although the response rates for N-MF and ECH were the same, indicating a similar degree of general anti-tumor activity as evaluated by the assay, N-MF showed greatest activity against lung tumors whereas ECH was more active against ovarian tumors. Twenty-six of 69 tumors (38%) were unresponsive to all drugs tested, only one tumor was responsive to both N-MF and ECH and no tumors were responsive to either N-MF or ECH alone. Cytoxan, one of the standard agents tested concurrently with both phase I drugs yielded a response rate of 35%, one and one-half times greater. Cervical and renal cancers and lymphomas were relatively unresponsive to both drugs.

Chemotherapy responsiveness of human tumors as first transplant generation xenografts in the normal mouse: six-day subrenal capsule assay.

Feasibility of utilizing human tumors as first transplant generation xenografts in the normal immunocompetent mouse for determining tumor sensitivity to chemotherapeutic agents was demonstrated by applying subrenal capsule (SRC) assay methodology to fresh surgical explants in a six-day time frame. A total of 37 human breast tumors were tested in assays in which 254 xenografts were implanted into control animals. Fifty (20%) of the controls showed some degree of partial regression in the six-day assay period. Using a mean control growth having a positive change in tumor size as the criterion for evaluability, first transplant generation human breast tumors provided an evaluable assay rate of 86%. A tumor response profile was obtained as a result of testing seven clinically active drugs against 32 previously untreated breast cancers. The pattern of responses obtained indicated that no single agent was active against all tumors, nor were tumors which were responsive to one agent necessarily responsive to another, suggesting the feasibility of predicting individual tumor response to specific chemotherapeutic agents. Had these seven drugs been developmental agents of unknown activity which were being tested for the first time against such a panel of human tumors the result would have not only predicted their clinical activity, but the tumor response rates would have also provided an indication of the relative potential of each drug for the specific treatment of breast cancer.

Growth of human tumor xenografts implanted under the renal capsule of normal immunocompetent mice.

The subrenal capsule technique proved effective in demonstrating that the growth of human tumors in normal, immunocompetent animals for 6 days was quantifiable in ocular micrometer units. Positive growth was demonstrable not only with human tumors that had been established in serial transplantation in athymic nude mouse hosts, but also with primary surgical explants. Growth rates of transplantation-established xenograft systems were similar whether implanted in athymic nude or in normal immunocompetent animals indicating that the 6-day time-frame successfully evades growth inhibitory effects of immunologic origin. Immunosuppression with a single dose of cyclophosphamide did not appear to affect growth rate, but permitted the tumors to grow larger extending the time to reach peak size. Significantly, xenografts of primary surgical explants showed positive growth more frequently in 6 days (82%) in the immunocompetent animal than in 11 days (30%) in the immunodeficient athymic nude mouse.