Potentiation of enteral absorption of human interferon alpha and selective transfer into lymphatics in rats

Lymph-directed immunotherapy - Harnessing endogenous lymphatic distribution pathways for enhanced therapeutic outcomes in cancer

The advent of immunotherapy has revolutionised the treatment of some cancers. Harnessing the immune system to improve tumour cell killing is now standard clinical practice and immunotherapy is the first line of defence for many cancers that historically, were difficult to treat. A unifying concept in cancer immunotherapy is the activation of the immune system to mount an attack on malignant cells, allowing the body to recognise, and in some cases, eliminate cancer. However, in spite of a significant proportion of patients that respond well to treatment, there remains a subset who are non-responders and a number of cancers that cannot be treated with these therapies. These limitations highlight the need for targeted delivery of immunomodulators to both tumours and the effector cells of the immune system, the latter being highly concentrated in the lymphatic system. In this context, macromolecular therapies may provide a significant advantage. Macromolecules are too large to easily access blood capillaries and instead typically exhibit preferential uptake via the lymphatic system. In contexts where immune cells are the therapeutic target, particularly in cancer therapy, this may be advantageous. In this review, we examine in brief the current immunotherapy approaches in cancer and how macromolecular and nanomedicine strategies may improve the therapeutic profiles of these drugs. We subsequently discuss how therapeutics directed either by parenteral or mucosal administration, can be taken up by the lymphatics thereby accessing a larger proportion of the body's immune cells. Finally, we detail drug delivery strategies that have been successfully employed to target the lymphatics.

Development of Interferon Suppositories. I. Enhanced Rectal Absorption of Human Fibroblast Interferon by Fusogenic Lipid via Lymphotropic Delivery in Rats

We attempted to enhance the rectal absorption of human fibroblast interferon (HuIFN-β) in rats by the administration of suppositories containing fusogenic lipid and a nontoxic surfactant. Suppositories containing either the lipid (linoleic acid) or the surfactant [HCO60; polyoxyethylated (60 mol) hydrogenated castor oil] alone failed to enhance the absorption of HuIFN-β. However, suppositories containing both linoleic acid and HCO60 facilitated the rectal absorption of HuIFN-β. The absorbed HuIFN-β was selectively delivered via the lymph.

Recombinant human interferon alpha-2a: delivery to lymphoid tissue by selected modes of application

The effect of different parenteral administration routes (i.d., s.c., i.v.), infusion rates, and albumin contents of the drug vehicle on the cumulative recovery of recombinant human interferon alpha-2a (rIFN alpha-2a) in lymph and on its concentration in blood and lymph was determined in sheep. Blood samples were withdrawn from a jugular vein catheter and lymph was collected from a cannulated efferent popliteal lymphatic duct. The concentration of rIFN alpha-2a in lymph and blood plasma samples was measured by an enzyme immunoassay. Following i.v. infusion of 2 x 10(7) U of rIFN alpha-2a, the peak concentrations measured in blood plasma and lymph, respectively, were 8250 and 14 U/ml. The concentration measured in lymph after i.d. or s.c. administration of the same dose was about 10(5) times higher (peak concentration, 3.1 x 10(6) U/ml), while blood plasma levels remained low (peak concentration, 315 U/ml). The cumulative recovery of rIFN alpha-2a in lymph following i.d. or s.c. administration was 59.2 +/- 7% (mean +/- SD; N = 8) and was affected neither by the infusion rate nor by the coadministration of albumin. Our data indicate that following i.d. or s.c. administration, rIFN alpha-2a (MW 19,000) is absorbed mainly by the lymphatics. This results in high levels of rIFN alpha-2a in the lymph which drains from the application site to the regional lymph nodes. The knowledge gained in this investigation may help to improve the mode of administration and therapeutic efficacy of protein drugs whose targets are lymphoid cells.