In China, the Conditional Approval process allows for new drugs to be marketed and developed based on an urgent and unmet need. For example, drugs which treat patients with rare or critical conditions could be granted conditional approval, allowing them to reach patients quicker. According to Pharmaceutical Technology, this is what happened with pamiparib, a treatment discovered and developed by biopharmaceutical company BeiGene. The treatment is designed for patients with Fallopian tube cancer, primary peritoneal cancer, and epithelial ovarian cancer. 

Pamiparib

According to BeiGene, pamiparib is:

an investigational small molecule inhibitor of PARP1 and PARP2. Pamiparib is being evaluated as a monotherapy in pivotal clinical trials in China in recurrent platinum-sensitive and BRCA1/2 mutated ovarian cancers, [and] as a monotherapy, and in combination with other agents, including BeiGene’s investigational anti-PD1 antibody, tislelizumab (BGB-A317), for a variety of solid tumor malignancies.

Both PARP1 and PARP2 play a role in cell survival and DNA repair. By inhibiting PARP1 and PARP2, pamiparib works to prevent DNA repair in relation to tumors.

The recent conditional approval hinged on data from a Phase 2 clinical trial. Altogether, 113 patients enrolled. Patients either had:

• Primary peritoneal cancer
• High-grade, non-mutinous, epithelial ovarian cancer
• Fallopian tube cancer (tubal cancer)

Enrolled patients had gBRCA gene mutations and had previously been treated with at least two or more lines of chemotherapy. Altogether, the final research consists of data from 101 of the 113 patients (89%). Researchers found pamiparib to be relatively safe, effective, and well-tolerated. Approximately 68.3% of patients displayed an objective response rate. Additionally, responses were sustained over a one-year period.

Pamiparib is orally administered. During treatment, patients receive 60mg pamiparib 2x each day. Altogether, BeiGene hopes to have pamiparib in patients’ hands by the end of May 2021.

Rare Cancers Treated by Pamiparib

Ovarian Cancer

As the name suggests, ovarian cancer forms in the ovaries, almond-shaped organs on either side of the uterus. The ovaries store eggs and produce estrogen and progesterone, two types of hormones. There are four subtypes of ovarian cancer which depend on where in the ovary (or ovaries) the cancer forms. First, an estimated 90% of ovarian cancer diagnoses are epithelial tumors which form in the thin tissue that covers the ovaries. Next, germ cell carcinoma tumors, which make up 5% of diagnoses, begin in the cells which form the eggs. Third, stromal carcinoma tumors consist of another 5% of diagnoses. These tumors form in the connective tissues which produce the hormones. Finally, small cell carcinoma of the ovary (SCCO) is the rarest form, accounting for only 0.1% of diagnoses.

Additionally, ovarian cancer progression occurs in four stages. During the first stage, cancer is found in one or both ovaries. By stage II, ovarian cancer has spread, usually to the pelvis. In the third stage, the cancer has metastasized to both the pelvis and abdomen. Finally, in stage IV, the cancer has spread throughout the body. Typically, this encompasses the lymph nodes, liver, lungs, or even bowel and bladder linings. Risk factors for ovarian cancer include BRCA gene mutations.

Symptoms, which may not appear until later stages, include:

• Pelvic pain
• Abdominal bloating and/or distention
• Appetite loss
• Menstrual irregularities
• Increased or abnormal vaginal discharge or bleeding
• Changes in urinary urgency or frequency
• Breast tenderness
• Endometrial hyperplasia

Learn more about ovarian cancer.

Fallopian Tube Cancer

Also known as tubal cancer, Fallopian tube cancer is an extremely rare gynecological cancer. In fact, only 1-2% of gynecological cancer doses consist of tubal cancer. As the name suggests, Fallopian tube cancer forms in the Fallopian tubes which connect the ovaries and uterus. Typically, the cancer forms elsewhere and metastasizes to the Fallopian tubes. However, the cancer can, in rare cases, begin there. Risk factors include age (60+), being Caucasian, being 50-60 and never having children, a family history of cancer, and BRCA gene mutations. However, birth control pills and having birthed children lower the risk of Fallopian tube cancer. Symptoms include:

• Abnormal vaginal bleeding
• Pink, white, or blood-tinged vaginal discharge
• Fatigue
• Changes in urinary urgency or frequency
• Abdominal pain or swelling
• Bloating
• Pelvic pressure
• Indigestion
• Painful intercourse

Learn more about Fallopian tube cancer from the MD Anderson Cancer Center.

Primary Peritoneal Cancer (PPC)

Primary peritoneal cancer (PPC) is a rare cancer which forms in the peritoneum, or the thin layer of epithelial tissue lining the abdomen, uterus, rectum, and bladder. Unlike cancer which begins elsewhere and spreads to the peritoneum, PPC begins there. PPC is more common in females than males. Other risk factors include being over 60 years old and having BRCA gene mutations. In many cases, PPC symptoms do not appear until later stages. When symptoms do appear, they include:

• Nausea and vomiting
• Appetite loss
• Diarrhea or constipation
• Feelings of fullness
• Shortness of breath
• Intestinal blockages
• Frequent urination
• Rectal or vaginal bleeding
• Unintended weight loss or weight gain
• Abdominal pain, pressure, or bloating