A couple of weeks ago, the Drug and Device Law Dog Walker texted us midday to report that a coyote had been spotted in our suburban neighborhood and that we should be vigilant when the Drug and Device Law Little Rescue Dogs were out in the yard. We scoffed, insisting that it must have been the neighborhood fox, known to all for years (we live right next to Valley Forge National Park).  The conversation went back and forth for a while, eventually including descriptions of larger size, different coloration, and much longer legs than the fox’s.  We remained unconvinced.  Eventually, our neighborhood e-mail chain came alive with close-up photos of what was undeniably a coyote, taken a scant hundred yards away in a neighbor’s back yard.   Because we are law nerds, it occurred to us that coyotes are just like causation:  an expert can assert a causal link, and assert it again, but, ultimately, there has to be evidence to support the assertion.

As the court agreed in today’s case, a nice (albeit unreported) affirmance of a HUMIRA summary judgment victory out of Maryland’s Court of Special Appeals. In Larson v. Abbott Labs., Inc., 2018 WL 3479236 (Md. Ct. Spec. App. July 19, 2018), the plaintiff, a highly-educated space engineer who had been diagnosed as HIV-positive years before, alleged that the defendant’s psoriasis medication caused him to become sufficiently immunocompromised that he contracted progressive multifocal leukoencephaly (PML).  PML is an often-fatal viral brain disease that left the plaintiff physically disabled and cognitively impaired, and unable to care for himself.  PML is caused by a virus that that is present in the bodies of most adults in the United States but that generally remains inactive except in severely immunocompromised people. HUMIRA’s prescribing information warned that medications of its class had the potential to affect defenses against infection, and that the safety and efficacy of the medication in immunosuppressed patients had not been evaluated.  The warnings did not specifically mention HIV patients.

The plaintiff had been diagnosed as HIV-positive five years before he took HUMIRA. During that time, he treated his plaque psoriasis with home remedies.  When it worsened, he asked his treater about treatment with HUMIRA.  She sought information from the defendant, then referred the plaintiff to a physician who concluded from the information that, because the plaintiff’s HIV was well controlled and that he was not severely immunocompromised (and because a tuberculosis skin test came back negative), he was an appropriate candidate for the medication.  What was unknown to the doctor – and apparently to the plaintiff – was that recent lab results revealed progression of his HIV disease.   (The plaintiff’s infectious disease specialist had attempted to contact him with the results, but he hadn’t responded by the time he began his HUMIRA treatment.) Within three months after beginning his treatment, he began exhibiting headaches and extreme fatigue.  His condition worsened, and he was diagnosed with PML shortly thereafter.

The plaintiff filed suit, asserting the usual product liability claims. His primary causation expert was a “highly-regarded infections disease specialist with significant experience” treating HIV-positive patients. Larson, 2018 WL 3479236 at *7.  The defendant moved to exclude the expert’s opinion.  The trial court granted the motion, and, because the plaintiff was left without expert causation testimony, the court granted summary judgment for the defendant.  The plaintiff appealed.

The plaintiff presented several questions for the appellate court’s determination, including questions related to the trial court’s holdings about the adequacy of the product’s warnings. The appellate court found that it needed to consider only one question – whether the trial court erred in barring the testimony of the plaintiff’s general and specific causation experts and granting summary judgment – because a negative answer to that question obviated the need to consider any of the others.  In the process, the court rejected the plaintiff’s argument that the it needed to address the adequacy of the warnings whether or not the plaintiff could establish medical causation.  As the court explained,

Generally, the “proximate causation element” in a failure to warn case against a pharmaceutical manufacturer is established by proof that the allegedly inadequate warning was a substantial contributing factor to the plaintiff’s injury. . . . In certain product liability cases, however, such as the case before us, the parties disagree over whether sufficient evidence exists to show that the product, itself, can cause the specific injury alleged and, therefore, whether the manufacturer had a duty to provide different or additional warning to prevent the injury. . . . . What is often termed “general causation” is present “when a substance is capable of causing a given disease. . . . General causation, therefore, relates to the element of duty — i.e., whether the risk of the type of injury the plaintiff suffered was reasonably foreseeable, and therefore, whether the manufacturer had a duty to warn the prescribing physician in the first place. . . . Evidence demonstrating [medical] causation . . . must exist independent of whether the manufacturer’s allegedly defective warning label was a proximate cause of the injury. In other words, evidence of general and specific causation was necessary in this case to establish [the defendant’s] duty to warn . . . .

Id., at *9-10. And so the court proceeded to determine whether the trial court had erred in excluding the plaintiff’s causation experts. The plaintiff’s causation theory was that “the immunosuppressant effect of HUMIRA permitted the ‘unmasking’ of [the virus that causes PML], despite the fact that” the plaintiff was not as immunosuppressed as HIV-positive patients who develop PML” even in light of his most recent lab results.  Id.  Maryland is a Frye state.  Under that standard, as the court explained, an expert’s opinion is admissible only if the basis of the opinion is “shown to be generally accepted as reliable within the expert’s particular scientific field.” Id. at *12 (internal punctuation and citations omitted). The standard applies equally to new scientific techniques and to accepted methods applied to support novel theories.

With respect to plaintiff’s main causation expert, the trial court had held that his causation conclusions “[had] not been sufficiently tested and proven to qualify as reliable forensic conclusions rather than scientific hypothesis.” Id. at *13.   The expert’s primary contention was that, “in addition to general HIV disease progression, some additional functional immune deficit must be present for PML to occur,” and that HUMIRA caused that deficit in the plaintiff. Id.   The trial court held that the expert had not considered other potential contributing factors, and that he could not provide a sufficient factual basis for his opinion that HUMIRA was “the missing link.” Id. at *14.

The appellate court stated that, “to constitute a sufficient basis for his general causation opinion, Dr. Jacobson needed to provide support for his contention that” the class of drugs was “known to be associated with an increased risk of PML” at the time the plaintiff took the drug. Id. The plaintiff contended that this support was to be found in the expert’s reference to the drug’s black-box warning about opportunistic pathogens coupled with “well-documented reports of PML occurring in patients who had received” this class of drugs.” Id. But, the court pointed out, the expert did not discuss the “well-documented reports of PML” or explain how the reports helped form the basis of his opinion.   The plaintiff also asserted that the expert relied on “peer reviewed studies, reviews of other biologicals, and FDA Adverse Event Reporting data,” but, the court found, he did not explain how the existence of case reports demonstrated a causal connection, and, the one article he cited related to a drug with a different mechanism of action than HUMIRA’s.

The court echoed the trial court’s holding that there “is sound scientific reasoning to suggest that [the drug’s immunosuppressive effect] could be a factor, but it falls short of showing with any degree of reliability that it is a factor, much less a substantial contributing cause” of the plaintiff’s PML. Id. at *15 (emphasis in original).   The court also reviewed the depositions of the plaintiff’s other experts, and held that, although they “believed that [the plaintiff’s] use of HUMIRA likely contributed to his immunological decline, none could provide a sufficient factual basis for that conclusion. . . . Indeed, [one] conceded that a scientifically reliable causal association” had not been established, id., and another stated “more unequivocally that he believed that [the plaintiff’s increased immunosuppression]” occurred “independent of HUMIRA, representing progression of his HIV disease.”  The same expert discussed an article establishing “the theoretical possibility” that the class of drugs was associated with PML, but explained that “it [didn’t] necessarily establish causation . . . .” Id.

The court commented that it agreed with the trial court that “it may well be that additional research will confirm some or all of [the expert’s] hypotheses. What is determinative in this case, however, is that those causal theories have not been established now nor were they established” when the plaintiff took the drug.  The court also acknowledged that there were ethical obstacles to conducting controlled studies on HIV-positive individuals, and that, because PML is a rare disease, “the amount of epidemiological data that could be useful is limited.”  But this didn’t excuse the experts’ theoretical causation opinions.  The court concluded, “We hold that [the plaintiff’s] experts’ opinions were not grounded on an adequate supply of data, and, therefore, the circuit court properly excluded their testimony.” Id. at *16,

We love a good expert exclusion. BTW, the coyote pictures are really cool.  E-mail us, and we will send them to you.