Daubert rulings can make for tough sledding. The best of them often wallow in drug- or plaintiff-specific facts, so even the nicest result is both hard to describe and tough to apply as precedent in cases involving other drugs.

Perry v. Novartis Pharmaceuticals Corp., No. 05-5350, 2008 WL 2683047 (E.D. Pa. July 9, 2008), is no exception. In his 40-page opinion, Judge Dalzell describes at length the animal studies, case reports, results of clinical trials, and biological hypotheses arguably linking Elidel (a cream used to treat eczema) with a form of non-Hodgkins lymphoma (“NHL”), which Andreas Perry developed at age two.

Judge Dalzell also describes what’s needed for an appropriate differential diagnosis to rule in a medication as a cause of disease when most cases of the disease have no known cause. Ultimately, Judge Dalzell concludes that one of the two plaintiff’s experts presented a reliable opinion on general causation, but that neither proved specific causation. The court granted Novartis’ motion to exclude plaintiffs’ experts, which then resulted in a grant of summary judgment.

The science surrounding Elidel interests those involved in that particular litigation, but we read the opinion with an eye toward finding the broader principles that may apply in later cases. And we found a few.

When analyzing the existing epidemiological evidence, one expert chose to focus on aggregate data about lymphomas in general, rather than particularized data about any link between the drug and non-Hodgkins lymphoma, which was the disease involved in the case. “It therefore appears that Dr. Smith’s analysis of the i3 report focused not on the findings that were most relevant to the hypothesis he sought to test but on the findings that were most helpful to his paying client. While this approach is, sadly, not uncommon, it is incompatible with the reliable application of the scientific method.” Slip op. at 23-24.

In what is perhaps the most helpful language in the opinion, the court goes on to explain that plaintiffs bear the burden of proof in product liability cases and so cannot prevail in the absence of data supporting their claims:

“Before we examine those studies, however, we must make clear that the non-existence of good data does not allow expert witnesses to speculate or base their conclusions on inadequate supporting science. In cases where no adequate study shows the link between a substance and a disease, expert testimony will generally be inadmissible, even if there are hints in the data that some link might exist. This may mean that early victims of toxic torts are left without redress because they are unable to prove their cases with the scientific data that exists. While this is a regrettable result in those individual cases, it is an unavoidable reality of the structure of our legal system and is necessary to protect the interests of defendants who might otherwise be subject to crippling verdicts on the basis of slender scientific evidence.”

Id. at 28.

Finally, the court turned to specific causation. “Here, the differential diagnoses . . . fail to exclude — much less address . . . — the likelihood that Andreas Perry’s lymphoma had no known cause. . . . [M]ost NHL cases and, more specifically, most T-LBL cases, are idiopathic, having no known cause. . . . Faced with similar situations, our sister courts have excluded experts’ differential diagnoses where they failed to adequately account for the likelihood that the disease was caused by an unknown factor.” Id. at 31-32.

The court went on to suggest ways that plaintiffs could overcome this hurdle, but held that “analysis beyond a differential diagnosis will likely be required.” Id. at 33.

Last, but not least, a helpful word on dosage: “The failure to address the issue of dosage in a scientific manner is just one more reason to conclude that plaintiffs’ experts did not reach their conclusions on the basis of the scientific method.” Id. at 38.

Perry is an impressive opinion, reflecting careful thought on a host of scientific issues. We’re pleased to see a federal judge wrestle so conscientiously with issues as hard as these.