Last year, I had the occasion in two prior posts (here and here) to highlight a new agent called amrubicin that is being studied in relapsed SCLC. At an ASCO conference where most of the news in SCLC was disappointing, amrubin studies again appeared promising.

The first of these studies was reported by Dr. David Ettinger at Johns Hopkins University (abstract here). This trial enrolled 75 patients who all had refractory disease, meaning that they had shown progression within 90 days of completing first line chemo) to receive amrubicin at 40 mg/m2 IV on days 1-3 every 21 days. In fact, the median time of being off chemo was only 38 days before starting amrubicin, which is associated with what we'd expect to be a low probability of benefiting much from more chemo. The response rate in the trial was 17.4%, well below the impressive response rates in the 50% range seen in Japan (where amrubicin is commercially available now, I believe), but in this setting of refractory patients, any responses are seen as pretty encouraging. The median progression-free survival was 3 months. Side effects were not a significant problem, with 62% of patients experiencing moderate to severe neutropenia (decreased white blood cell counts), a very common side effect of chemotherapy, and no significant heart toxicity, which has been a concern about this class of chemotherapy drugs (called anthracyclines).

It's hard to put these results into any context without something to compare the amrubicin results to. Fortunately, two other trials presented at ASCO randomized relapsed SCLC patients to either topotecan, which is an approved standard of care for this setting, or amrubicin. One of these trials was done by the North Japan Lung Cancer Study Group (abstract here), which randomized 59 patients with either sensitive ( at least 90 days between completing first line chemo and progression) or resistant SCLC (<90 days to progression) to either topotecan (lower dose than the FDA-approved regimen) or amrubicin. All of the endpoints favored amrubicin: response rate was 38% vs. 13%, with results much better for both in sensitive patients (53% vs. 21%) than in resistant patients (17% vs 0%); and progression free survival was also better with amrubicin (3.5 vs. 2.2 months). Both drugs caused significant transient drops in blood counts, overall pretty comparable between the two groups, with a little more febrile neutropenia in the amrubicin group (14% vs. 3%).

The other randomized trial was based in the US and reported by Jotte and colleagues (abstract here). It randomized 76 patients, all with sensitive disease, in a 2:1 fashion, so 2/3 of the patients received amrubicin and 1/3 received topotecan. Again, amrubicin appeared clearly superior, with a response rate of 34% vs. 3.8%, and a median progression-free survival of 4.6 vs. 3.5 months. And with the higher, standard approved dose of topotecan, the drops in blood counts were overall more significant with topotecan, notably in terms of neutropenia and low platelets.

To me, amrubicin appears to be the most promising investigational agent in SCLC right now (at least investigational here in the US). There are several clinical trials with amrubicin that are ongoing, including a larger one comparing amrubicin to topotecan in relapsed SCLC and another in the first line setting that is directly comparing cisplatin/amrubicin to cisplatin/etoposide. There's more information about amrubicin in SCLC clinical trials here.