CHICAGO ( TheStreet) -- There's some confusion over the spark that's causing Clovis Oncology ( CLVS) shares to double in value today. The company has presentations on two cancer drugs at the big American Society of Clinical Oncology (ASCO) annual meeting but it's the lung cancer drug -- CO-1686 -- which has set Wall Street heart fluttering. J.P. Morgan analyst Cory Kasimov told clients this morning that the CO-1686 data were "extremely impressive." In our first real look at Phase 1/2 efficacy data for the irreversible EGFRm inhibitor, the drug showed 4 confirmed partial responses (PRs) in heavily pre-treated T790M+ NSCLC pts, and they may not yet even be close to the maximum tolerated dose (MTD). In addition, 3/4 evaluable T790M+ patients treated at 900 mg BID (highest dose to date) achieved PRs. There were no clear investor expectations going in, but we strongly believe this is better than anyone's best case. Indeed, we see this as unprecedented activity in this patient population (and at what may still be a suboptimal dose). Emphasis Kasimov's. Clovis shares are up $37.98, or 104%, to $74.56 in afternoon trading. Clovis is also developing rucaparib, a PARP inhibitor. Phase I data in ovarian and breast cancer were presented at ASCO today. Biomarin ( BMRN) and Tesaro ( TSRO) have competing PARP inhibitors in clinical trials. Rucaparib is playing a role in Clovis' big stock move today, but the real push is due to CO-1686 because there is no currently approved treatments for lung cancer patients with the T790M mutation. -- Reported by Adam Feuerstein in Boston. Follow Adam Feuerstein on Twitter.