Tumor targeting by covalent conjugation of a natural fatty acid to paclitaxel.

Certain natural fatty acids are taken up avidly by tumors for use as biochemical precursors and energy sources. We tested in mice the hypothesis that the conjugation of docosahexaenoic acid (DHA), a natural fatty acid, and an anticancer drug would create a new chemical entity that would target tumors and reduce toxicity to normal tissues. We synthesized DHA-paclitaxel, a 2'-O-acyl conjugate of the natural fatty acid DHA and paclitaxel. The data show that the conjugate possesses increased antitumor activity in mice when compared with paclitaxel. For example, paclitaxel at its optimum dose (20 mg/kg) caused neither complete nor partial regressions in any of 10 mice in a Madison 109 (M109) s.c. lung tumor model, whereas DHA-paclitaxel caused complete regressions that were sustained for 60 days in 4 of 10 mice at 60 mg/kg, 9 of 10 mice at 90 mg/kg, and 10 of 10 mice at the optimum dose of 120 mg/kg. The drug seems to be inactive as a cytotoxic agent until metabolized by cells to an active form. The conjugate is less toxic than paclitaxel, so that 4.4-fold higher molar doses can be delivered to mice. DHA-paclitaxel in rats has a 74-fold lower volume of distribution and a 94-fold lower clearance rate than paclitaxel, suggesting that the drug is primarily confined to the plasma compartment. DHA-paclitaxel is stable in plasma, and high concentrations are maintained in mouse plasma for long times. Tumor targeting of the conjugate was demonstrated by pharmacokinetic studies in M109 tumor-bearing mice, indicating an area under the drug concentration-time curve of DHA-paclitaxel in tumors that is 8-fold higher than paclitaxel at equimolar doses and 57-fold higher at equitoxic doses. At equimolar doses, the tumor area under the drug concentration-time curve of paclitaxel derived from i.v. DHA-paclitaxel is 6-fold higher than for paclitaxel derived from i.v. paclitaxel. Even at 2 weeks after treatment, 700 nM paclitaxel remains in the tumors after DHA-paclitaxel treatment. Low concentrations of DHA-paclitaxel or paclitaxel derived from DHA-paclitaxel accumulate in gastrocnemius muscle; which may be related to the finding that paclitaxel at 20 mg/kg caused hind limb paralysis in nude mice, whereas DHA-paclitaxel caused none, even at doses of 90 or 120 mg/kg. The dose-limiting toxicity in rats is myelosuppression, and, as in the mouse, little DHA-paclitaxel is converted to paclitaxel in plasma. Because DHA-paclitaxel remains in tumors for long times at high concentrations and is slowly converted to cytotoxic paclitaxel, DHA-paclitaxel may kill those slowly cycling or residual tumor cells that eventually come into cycle.

Tumor targeting by conjugation of DHA to paclitaxel.

Targeting an anti-cancer drug to tumors should increase the Area Under the drug concentration-time Curve (AUC) in tumors while decreasing the AUC in normal cells and should therefore increase the therapeutic index of that drug. Anti-tumor drugs typically have half-lives far shorter than the cell cycle transit times of most tumor cells. Tumor targeting, with concomitant long tumor exposure times, will increase the proportion of cells that move into cycle when the drug concentration is high, which should result in more tumor cell killing. In an effort to test that hypothesis, we conjugated a natural fatty acid, docosahexaenoic acid (DHA), through an ester bond to the paclitaxel 2'-oxygen. The resulting paclitaxel fatty acid conjugate (DHA-paclitaxel) does not assemble microtubules and is non-toxic. In the M109 mouse tumor model, DHA-paclitaxel is less toxic than paclitaxel and cures 10/10 tumored animals, whereas paclitaxel cures 0/10. One explanation for the conjugate's greater therapeutic index is that the fatty acid alters the pharmacokinetics of the drug to increase its AUC in tumors and decrease its AUC in normal cells. To test that possibility, we compared the pharmacokinetics of DHA-paclitaxel with paclitaxel in CD2F1 mice bearing approximately 125 mg sc M109 tumors. The mice were injected at zero time with a bolus of either DHA-paclitaxel or paclitaxel formulated in 10% cremophor/10% ethanol/80% saline. Animals were sacrificed as a function of time out to 14 days. Tumors and plasma were frozen and stored. The concentrations of paclitaxel and DHA-paclitaxel were analyzed by LC/MS/MS. The results show that DHA targets paclitaxel to tumors: tumor AUCs are 61-fold higher for DHA-paclitaxel than for paclitaxel at equitoxic doses and eight-fold higher at equimolar doses. Likewise, at equi-toxic doses, the tumor AUCs of paclitaxel derived from i.v. DHA-paclitaxel are 6.1-fold higher than for paclitaxel derived from i.v. paclitaxel. The tumor concentration of paclitaxel derived from i.v. paclitaxel drops rapidly, so that by 16 h it has fallen to the same concentration (2.8 microM) as after an equi-toxic concentration of DHA-paclitaxel. In plasma, paclitaxel AUC after an MTD dose of DHA-paclitaxel is approximately 0.5% of DHA-paclitaxel AUC. Thus, the increase in tumor AUC and the limited plasma AUC of paclitaxel following DHA-paclitaxel administration are consistent with the increase in therapeutic index of DHA-paclitaxel relative to paclitaxel in the M109 mouse tumor model. A phase I clinical study has been completed at The Johns Hopkins Hospital to evaluate the safety of DHA-paclitaxel in patients with a variety of solid tumors. Twenty-one patients have been treated to date. The recommended phase II dose is 1100 mg/m(2), which is equivalent to 4.6 times the maximum approved paclitaxel dose on a molar basis. No alopecia or significant peripheral neuropathy, nausea, or vomiting have been observed. Asymptomatic, transient neutropenia has been the primary side effect. Eleven of 22 evaluable phase I patients transitioned from progressive to stable disease, as assessed by follow-up CT. Significant quality of life improvements have been observed. Thus, DHA-paclitaxel is well tolerated in patients and cures tumors in mice by targeting drug to tumors.

Guidelines for the organization of a blood transfusion service / edited by W. N. Gibbs, A. F. H. Britten / Pautas para la organización de un servicio de transfusión de sangre / L' Organisation d' un service de transfusion sanguine : principes directeurs

A comprehensive guide to the principles and procedures involved in establishing or reorganizing a national blood transfusion service in developing countries. Focusedon organizational principles rather than technical details, the book responds to both the growing clinical need for safe and effective blood products and the many problems inherent in the organization of a transfusion service. Guidelines and advice draw upon several clear examples of successes and failures taken from international experiences in the difficult process of establishing a new transfusion service. The objective is to provide information to decision-makers and planners on how to develop a correctly organized scheme of management, select equipment, establish standard procedures, and train staff so as to provide an adequate supply of blood and blood products which are as safe as possible and accessible at reasonable cost. To this end, cost-saving options are presented together with clear indications of areas where expense is inevitable and no short-cuts are possible. The book has nine chapters. The first introduces the main functions, responsibilities, and organizational options of a national transfusion service. Information includes a discussion of the importance of following a policy of voluntary blood donation, an outline of the strengths and weaknesses of different systems for organizing a transfusion service, and advice on how to calculate the staff needs and operating costs of a service. Readers are reminded that a blood transfusion service is an expensive and complex organization, that careful design and management are essential, and that a scheme for meeting recurrent costs needs to be in place. Subsequent chapters outline the guiding principles for planning a donor recruitment programme and discuss the procedures to be followed during blood collection. Details range from the simple observation that a U-shaped arrangement of donation beds increases staff efficiency to a series of 15 questions that can help ensure the safety of both donors and recipients. Of particular value is a chapter devoted to the screening of blood for hepatitis, AIDS, syphilis and yaws, malaria, Chagas disease, cytomegalovirus, and other transmissible diseases. Other chapters outline the organizational procedures that should guide the production of laboratory reagents at the national or regional level, the selection of methods for blood-grouping and compatibility testing, and the acquisition of basic equipment and consumables, moving from refrigerators and centrifuges to pipettes and marking pens. The book concludes with guidelines for quality assurance and biosafety, followed by an outline of clinical indications for the use of whole blood, red cells, plasma, platelets, cryoprecipitate, factor VIII concentrate, factor IX complex, albumin, and immunoglobulins

New product opportunities with DRGs.

Medicare's new payment scheme for hospitals and other cost-containment pressures have changed the way that hospitals do business. The number and duration of hospital patient admissions have declined. Hospitals are more carefully considering the cost of their supplies. As a result, demand for many types of hospital supplies has declined; however, new market conditions have also created opportunities for innovation in the device and pharmaceutical industry. This paper describes the new economic incentives for hospitals and how these translate into new product opportunities in the areas of outpatient care, less-invasive surgical procedures, decreasing length of stay in hospitals or substituting for high labor costs during hospital stays, and generally, products that provide the same quality of care as before but at much lower cost. Specific examples of such products from Rorer Group Inc. are chosen to illustrate the company's attempts to meet the new needs of the hospital marketplace.

Fusion of dipalmitoylphosphatidylcholine vesicles at 4 degrees C.

Small sonicated dipalmitoylphosphatidylcholine vesicles when incubated at 4 degrees C and high concentrations are shown to fuse completely to vesicles about 700-A diameter in 7 days, and these further fuse to about 950 A diameter vesicles after 3-4 weeks. The 950 A diameter vesicles are spherical, homogeneous, mostly unilamellar, have an internal aqueous space about 10 times that of small vesicles, and are stable for at least 6 months. The 950-A vesicles are characterized by agarose gel chromatography, freeze-fracturing electron microscopy, trapped volume measurements, differential scanning calorimetry, and diphenylhexatriene fluorescence polarization.