SAN FRANCISCO, CA, USA I November 20, 2014 I Nektar Therapeutics (NASDAQ: NKTR) today announced results of a study investigating the preclinical anti-tumor activity and tolerability of etirinotecan pegol (NKTR-102) in combination with the PARP inhibitor rucaparib in a BRCA1-deficient MX-1 breast tumor model. The preclinical study results demonstrated that all dose combinations of NKTR-102 and rucaparib were well-tolerated, synergistic, and led to 100% prolonged survival in this tumor model. These data were presented during the Symposium on Molecular Targets and Cancer Therapeutics in Barcelona, Spain, sponsored by the European Organisation for Research and Treatment of Cancer (EORTC), the National Cancer Institute (NCI) and the American Association for Cancer Research (AACR). 

“We are encouraged by these results which demonstrate that NKTR-102 in combination with the PARP inhibitor rucaparib has a synergistic effect resulting in 100% prolonged survival in a BRCA 1-deficient tumor model,” said Stephen K. Doberstein, Ph.D., senior vice president and chief scientific officer of Nektar Therapeutics. “As a next-generation topo-I inhibitor with broad anti-tumor activity, NKTR-102 has the potential to be combined with a number of targeted agents in multiple tumor settings.”

NKTR-102 is the first long-acting topoisomerase I inhibitor with an extended half-life and a unique structure that is also designed to concentrate the drug in tumors. In patients, NKTR-102 leads to greatly prolonged plasma SN38 exposure compared to irinotecan (elimination half-life of 50 days compared to 2 days) yet peak SN38 concentrations are at least 5- to 10-times less, which may also result in a favorable tolerability profile.

Preclinical Study Design and Results
Study investigators initiated tumor xenografts with MX-1 human breast carcinomas maintained by serial subcutaneous transplantation in female athymic nude (Crl:NU(Ncr)-Foxn1nu), 8-week-old mice. On the day of tumor implant, each test mouse received a 1-mm3 MX-1 fragment implanted subcutaneously in the right flank. Animals were randomized into treatment groups (n=10/grp) when their tumors reached 63-196 mm3 and subsequently received either vehicle, NKTR-102, rucaparab, or combinations of NKTR-102 + rucaparib. Doses selected were known to provide clinically relevant exposure levels. Twice weekly, animals were weighed, and tumor volumes were measured until the endpoint (2000 mm3 or Day 88) was met. Efficacy was measured by tumor growth delay and regression response rate.

NKTR-102 and rucaparib in combination exhibited marked synergy, demonstrated by durable complete responses, even at the lowest doses of both agents dosed in combination. The combination of NKTR-102 and rucaparib was tolerated at all dose levels. Doses used in this study provide exposures of NKTR-102 (SN38 trough) and rucaparib that are achievable clinically, underscoring the translational relevance of these results.

Combination studies of NKTR-102 and rucaparib are ongoing in patient-derived xenograft models in collaboration with Professor Paul Haluska at Mayo Clinic and Clovis Oncology.

About NKTR-102

NKTR-102 is currently being evaluated in a Phase 3, open-label, randomized, multicenter study called the BEACON study.  BEACON enrolled 852 women with locally recurrent or metastatic breast cancer, who have previously been treated with anthracycline, taxane or capecitabine (ATC), and is being conducted at approximately 150 sites worldwide including North America, Western Europe, Russia and the Republic of Korea. Nearly half of the patients enrolled in BEACON were located in North America. Patients were randomized on a 1:1 basis to receive 145 mg/m2 of single-agent NKTR-102 once every three weeks or a single agent of physician’s choice. The physician’s choice agents include: ixabepilone, vinorelbine, gemcitabine, eribulin, or a taxane. Randomization was stratified by geographic region, prior use of eribulin and receptor status.

The primary endpoint of the BEACON study is overall survival; secondary endpoints include progression-free survival, objective tumor response rates, clinical benefit rate, duration of response, pharmacokinetics, safety, quality-of-life measurements, and pharmacoeconomic implications. The study is also evaluating specific biomarker data to assess correlation with objective tumor response rates, progression-free survival, overall survival and selected toxicities.

About Nektar
Nektar Therapeutics has a robust R&D pipeline in pain, oncology, hemophilia and other therapeutic areas. In the area of pain, Nektar has an exclusive worldwide license agreement with AstraZeneca for MOVANTIKTM, the first FDA-approved once-daily oral peripherally-acting mu-opioid receptor antagonist (PAMORA) medication for the treatment of opioid-induced constipation (OIC), in adult patients with chronic, non-cancer pain. The AstraZeneca agreement also includes NKTR-119, an earlier stage development program that is a co-formulation of MOVANTIKTM and an opioid. NKTR-181, a wholly-owned mu-opioid analgesic molecule for chronic pain conditions, has completed Phase 2 development. NKTR-171, a wholly-owned new sodium channel blocker being developed as an oral therapy for the treatment of peripheral neuropathic pain, is in Phase 1 clinical development. In oncology, etirinotecan pegol (NKTR-102) is being evaluated in a Phase 3 clinical study (the BEACON study) for the treatment of metastatic breast cancer. In hemophilia, BAX 855, a longer-acting PEGylated Factor VIII therapeutic is in Phase 3 development conducted by partner Baxter. In anti-infectives, Amikacin Inhale is in Phase 3 studies conducted by Bayer Healthcare as an adjunctive treatment for intubated and mechanically ventilated patients with Gram-negative pneumonia.

Nektar’s technology has enabled nine approved products in the U.S. or Europe through partnerships with leading biopharmaceutical companies, including AstraZeneca’s MOVANTIKTM, UCB’s Cimzia® for Crohn’s disease and rheumatoid arthritis, Roche’s PEGASYS® for hepatitis C and Amgen’s Neulasta® for neutropenia.

Nektar is headquartered in San Francisco, California, with additional operations in Huntsville, Alabama and Hyderabad, India. Further information about the company and its drug development programs and capabilities may be found online at http://www.nektar.com.

SOURCE: Nektar Therapeutics