Pacira BioSciences, Inc. announced it has received a Paragraph IV Certification Notice Letter from The WhiteOak Group, a subsidiary of Chinese company Zhejiang Haichang Biotechnology Co Ltd, challenging the patent protection of its flagship pain management drug EXPAREL. The generic drug application represents a significant threat to Pacira's intellectual property portfolio and market exclusivity for its leading non-opioid analgesic.
Generic Challenge Targets 19 Patents
WhiteOak has filed an Abbreviated New Drug Application (ANDA) with the FDA for a product claiming to be a generic version of EXPAREL (bupivacaine liposome injectable suspension). In the notice, WhiteOak alleges that 19 EXPAREL patents listed in the FDA's Orange Book are "invalid, unenforceable and/or will not be infringed" by their proposed generic product.
The contested patents span two distinct patent families, with the first family expiring on January 22, 2041, and the second family expiring on July 2, 2044. The challenged patents include U.S. Patent Nos. 11,033,495, 11,179,336, 11,278,494, 11,304,904, 11,311,486, 11,357,727, 11,426,348, 11,452,691, 11,819,574, 11,819,575, 11,925,706, 12,144,890, 12,151,024, 12,156,940, 12,226,610, 12,251,468, 12,296,047, 12,318,483, and 12,370,142.
Legal Response and Timeline
Pacira intends to "vigorously assert and enforce its intellectual property rights" and has 45 days from receipt of the PIV Notice to file a lawsuit against WhiteOak. If Pacira chooses to pursue litigation, the lawsuit will trigger an automatic 30-month stay of FDA approval for WhiteOak's ANDA submission under the Hatch-Waxman statute, providing additional market protection for EXPAREL.
Notably, neither WhiteOak nor its parent company Zhejiang Haichang Biotechnology have any commercialized products, making this their first attempt to enter the U.S. pharmaceutical market through generic drug development.
EXPAREL's Clinical Profile and Market Position
EXPAREL represents the first and only multivesicular liposome local anesthetic approved for peri- and postsurgical use. The drug combines bupivacaine with multivesicular liposomes, a delivery technology that releases medication over an extended time period. EXPAREL is currently approved for infiltration and fascial plane blocks in patients aged 6 years and older, as well as specific nerve blocks in adults including interscalene brachial plexus, adductor canal, and sciatic nerve blocks in the popliteal fossa.
Clinical studies have demonstrated that a single dose of EXPAREL delivers bupivacaine over time, providing significant reductions in cumulative pain scores with up to a 78 percent decrease in opioid consumption, though the clinical benefit of the opioid reduction was not demonstrated in the studies.
Safety Considerations
The most common side effects of EXPAREL vary by administration method. For wound infiltration in adults, the most frequent adverse events are nausea, constipation, and vomiting. When administered via nerve block in adults, the most common side effects include nausea, fever, and constipation. In pediatric patients, side effects encompass nausea, vomiting, constipation, low blood pressure, decreased red blood cell count, muscle twitching, blurred vision, itching, and rapid heartbeat.
EXPAREL can cause temporary loss of sensation and muscle movement lasting up to five days, depending on the injection site and dosage. The drug is contraindicated for obstetrical paracervical block anesthesia and carries restrictions for use in patients under 6 years old for wound infiltration and under 18 years old for nerve blocks.
Broader Portfolio Context
Beyond EXPAREL, Pacira's commercial portfolio includes ZILRETTA (triamcinolone acetonide extended-release injectable suspension) for osteoarthritis knee pain management and iovera, a cryoneurolysis device for drug-free pain control. The company is also developing PCRX-201 (enekinragene inzadenovec), a locally administered gene therapy for osteoarthritis treatment.
