3-[(4-Methyl-1-piperazinyl)carbonyl]-7-oxabicyclo[2.2.1]heptane-2-carboxylic acid (LB-100) is an experimental cancer therapeutic with cytotoxic activity against cancer cells in culture and antitumor activity in animals. It is an intravenously administered, small-molecule, serine-threonine protein phosphatase (PP2A) inhibitor, being developed by Lixte Biotechnology Holdings. LB-100 delivers an active metabolite into the cell, potently inhibiting specifically the s/t ptases PP2A. Inhibition of PP2A markedly potentiates the effectiveness of standard anti-cancer drugs and X-ray that exert their clinical benefit by damaging DNA thereby inhibiting faithful cell division. Although the growth of normal cells including those of the bone marrow, GI tract, and hair is also impaired by cytotoxic cancer treatment, cancer cells often have acquired genetic damage that permits their unrestrained growth but also reduces their ability to repair DNA damage. Inhibition of PP2A by LB-100 further impairs DNA repair to a greater extent in the cancer cell than in the normal cell providing more selective killing. LB-100 used alone has modest inhibitory activity against many cancers in model systems, but certain human cancers, possessing unique genetic changes in addition to those reducing DNA damage repair, are particularly vulnerable to inhibition of PP2A by LB-100. Among these is myelodysplastic syndrome (MDS), an increasingly common neoplastic disease, especially in persons aged 65 and older, characterized by failure of the bone marrow. In particular, a variant of MDS termed del(5q)MDS is missing ~50% of its PP2A activity rendering this tumor potentially vulnerable to further pharmacologic inhibition of PP2A

Othera Pharmaceuticals originally developed OT-730 (now known as QLT 091568) as an oculoselective beta-blocker for reducing the elevated intraocular pressure associated with glaucoma. OT-730 was involved in phase II clinical trial in patients with ocular hypertension or open-angle glaucoma. However, these studies were discontinued. At December 30, 2009, QLT Inc. acquired OT-730.